Devices and methods for contacting living tissue

ABSTRACT

The present invention provides materials and methods for forming an interface between an appliance and living tissue using a foamed elastomeric material which contacts the tissue or similar surfaces. The elastomeric material is in the form of a durable and washable material that, when applied to or implanted in living tissue or similar surfaces, displaces and flows in to non-conforming areas creating an air and/or water tight seal that substantially returns to an original shape when removed from the contact surface. The appliance may also include structural elements designed to optimize comfort, compliance and seal achieved through minimizing the pressure variation along the contact surface of the therapy device.

The present application claims the benefit of U.S. ProvisionalApplication No. 62/817,522, filed Mar. 12, 2019, which is herebyincorporated by reference in its entirety including all tables, figures,and claims and from each of which priority is claimed.

BACKGROUND OF THE INVENTION

The following discussion of the background of the invention is merelyprovided to aid the reader in understanding the invention and is notadmitted to describe or constitute prior art to the present invention.

U.S. Pat. Nos. 5,343,878, 7,182,082, and 7,762,263 describe variousdevices which purport to utilize application of negative pressure uponthe external neck surface of patients. A therapeutic appliance istypically provided that has a surface which is configured to enclose anexternal area of the throat (the term “throat” as used herein referringto the anterior portion of the neck extending approximately from thechin to the top of the sternum and laterally to a point posterior to theexternal jugular vein) overlying a portion of the upper respiratorypassage. In certain embodiments, these appliances can provide a chamber(e.g., a hollow space filled with air molecules) lying between theinterior surface of the chamber and the throat. The therapy appliance isoperably connected to a vacuum source which is configured to produce apartial negative pressure in this chamber. Application of a therapeuticlevel of negative pressure in the chamber elicits movement of the upperairway and may alleviate conditions such as snoring, sleep apnea, andfull or partial airway collapse whether during sleep or when a patientis undergoing a medical procedure while under sedation for example.

It can be difficult to obtain a proper and comfortable fit between suchan apparatus and the patient to create and maintain the differentialnegative pressure (relative to atmospheric pressure for example) at thedesired location on the patient. In the case of devices intended fordaily wear for many hours, any points of high contact pressure from thedevice's sealing on the user's tissue soon become too uncomfortable forcontinued use. Further, success of these negative pressure therapies canbe determined by a device's ability to accommodate (flex, bend, flow,etc.) varying anatomical features (i.e. device compliance). Usercompliance with therapy is maximized by a good comfortable interfacebetween the device and the user, and by an interface that minimizes oreliminates tell-tale post-treatment red marks when the device isremoved. Finally, the device should optimally accommodate some stubblegrowth and/or movement to different sleeping positions without loss ofseal.

Similarly, masks adapted for infusion of a fluid, e.g., gas, to apatient, in particular those suffering from obstructive sleep apnea(OSA), are preferably designed to not only deliver the fluid, but alsoto seal well on the patient's face, to be adaptable with any patientmovement, and to be comfortable. Masks that are comfortable andcompliant but do not seal optimally are less effective. If the frame forthe mask is hard plastic, sealing and compliance must be provided by thefacial cushion. A very sensitive area of the face where seal is usuallylocated is the nasal bridge region. Any increase in pressure may bedirectly translated to the nasal bridge region, resulting in a fit thatis uncomfortable and even painful. Some masks had flowable-type gels atthe skin interface which were heavy and when the membrane was worn couldrupture and leak gel into the airways, creating a potential healthhazard.

While an enclosed gel is a good absorber of pressure (e.g., areas ofhigh contact pressure may be redistributed), it is not necessarily agood sealing medium, particularly when it lacks “compliance” (e.g., bynot being able to remain in intimate contact with the patient's skin dueto minor relative movement, such as experienced by natural bodymovement). Compliance is the level of displacement achievable betweenthe patient's face and cushion and/or the mask's ability to maintain acomfortable seal. ResMed's Activa™ cushion is an example of a cushionproviding very good compliance. The lack of compliance and resiliencemay affect seal performance and may create localized pressure pointssuch as on higher facial landmarks, especially the nasal bridge region.

Likewise, Filtering Face-piece Respirators (FFRs) play a critical rolein everyday life. They are available for purchase to the general publicin most hardware stores and are recommended, or required, for use in awide variety of home, public, and occupational environments—especiallyin healthcare settings. Their principal function is to providerespiratory protection against both non-biological and biologicalparticulates.

In practice, FFRs are used generally to protect the wearer. Inhealthcare institutions, and public health settings, however, FFRs mustfunction both to protect the wearer from potentially harmful particulatematter, including biological pathogens, and/or to protect patients andothers from the wearer exhaling pathogens into the environment. Duringsurgical procedures, for example, the smoke plume generated fromelectrosurgical use has been shown to contain a wide variety ofvaporized viral organisms capable of infection, including HIV and HumanPapilloma Virus (HPV). A FFR in such a setting must therefore protectthe surgeon and those in the operating room, while at the same timeprotecting the patient from the surgeon's exhaled pathogens coming intocontact with the surgical field.

With respect to sealing the mask to the wearer's face, the principalreason to achieve such a seal is to avoid leakage around the filterportion of the mask, as opposed to through the filter. This is true forboth inhaled and/or exhaled particulate matter coming from the user.Face Seal Inner Leakage (FSIL) as well as Face Seal Outer Leakage(FSOL), (collectively referred to as Face Seal Leakage (FSL)) isdifficult to reduce because of the significant variances in human facialanatomy. Anthropometric studies have revealed the substantialdifferences in the multiple variables of human facial anatomy. These arenotable, perhaps not coincidentally, in the three areas that are commonfor face seal leakage to occur: 1) the nasal bridge and the cheek bone,2) the cheek bone to the edge of the lower jaw, and 3) around and underthe area between the undersurface of the chin back toward the angle ofthe jaw. The problem of face seal leakage may also be compounded by FFRsbeing made in fairly generic “small, medium, and large” sizes, and oftensimply as a “one size fits all” design.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of the invention to provide an appliance designed to becontacted with living tissue, where a tissue interface region of theappliance is adapted to form a conforming seal between the appliance andthe tissue. In certain aspects, the appliance is configured to attachand seal to a patient's external or internal tissue, such as a face, aneck, an area surrounding a wound, etc.

As described hereinafter, the tissue interface region may comprise aninherent sticky or adhesive quality (referred to as “tack”) to improvethe sealing, resist sliding against tissue, and increase the breadth ofanatomical differences that the therapy device will accommodate tosecure an appropriate seal and or fit. Tack may be influenced, forexample, by the mix ratio of “two component” starting materials or bythe addition of tackifiers.

In a first aspect, the invention provides an appliance configured tocontact animal, preferably mammalian, and most preferably human, tissue,comprising:

(a) a tissue interface portion comprising a viscoelastic foam configuredto provide a tissue contact surface of the appliance, wherein theviscoelastic foam comprises one or more of the following properties:

-   -   a Shore A of about 0 or less, and preferably a Shore 00        durometer of about 30 or less, more preferably of about 20 or        less, and still more preferably of about 10 or less, in each        case as measured using the Standard Test Method for Rubber        Property—Durometer Hardness ASTM D2240-15;    -   a density (specific gravity) of about 0.9 g/cm³ or less; and/or    -   a level of tack measured using the Standard Test Method for        Pressure-Sensitive Tack of Adhesives ASTM D2979-16 of about 9        mJ/cm² or less, preferably about 7 mJ/cm² or less, most        preferably about 5 mJ/cm² or less;    -   an elastic (storage) modulus of between about 0.3 kPa to about        30 kPa, and preferably between about 1 kPa and about 15 kPa;    -   a viscous (loss) modulus of between about 0.4 kPa to about 7        kPa, and preferably between about 0.8 kPa and about 7 kPa; and        (b) a non-contacting portion configured to support the tissue        interface portion and to be separated from the tissue by the        tissue interface portion.

The term “viscoelastic” as used herein refers to materials that exhibitboth viscous and elastic characteristics when undergoing deformation.Unlike purely elastic substances, a viscoelastic substance has anelastic component and a viscous component. The viscosity of aviscoelastic substance gives the substance a strain rate dependence ontime. Purely elastic materials do not dissipate energy (heat) when aload is applied, then removed. However, a viscoelastic substance losesenergy when a load is applied, then removed.

The storage and loss modulus in viscoelastic materials measure thestored energy, representing the elastic portion, and the energydissipated as heat, representing the viscous portion. The storage (E′)and loss (E′) moduli are measured in KPa using Dynamic MechanicalAnalysis (DMA) methods known in the art. In certain embodiments, theviscoelastic foam comprises one or both of an elastic (storage) modulusof between about 10 kPa and about 15 kPa and a viscous (loss) modulus ofbetween about 2 kPa and about 7 kPa.

The term “tissue” as used herein refers to a collection of cells. Tissuecan include, and in some embodiments preferably includes, cells thatgrow and/or reproduce. Tissue can comprise a layer of cells that are notliving, such as skin which comprises a stratum corneum layer overlyingthe living cells of the tissue. Tissue is preferably a part of amammalian, and most preferably human, body.

The term “non-contacting portion” as used herein refers to portions ofthe appliance that are not in direct contact with the tissues of theuser. Such a portion may be, for example, the interior of an appliancethat is implanted within in a user's body, or may be the exterior of anappliance that is worn on the body. The non-contacting portion may beunitary or integral with the tissue interface portion. By way ofexample, if the entire appliance is made from the viscoelastic foam,then the portions of the foam that are not in direct contact with thetissues of the user are said to be non-contacting. In preferredembodiments, however, the non-contacting portion comprises materialother than the viscoelastic foam and can therefore be conceptuallythought of as a different component from the tissue interface portion.

In certain embodiments, the viscoelastic foam exhibits a Shore Adurometer of about 10 or less, preferably about 5 or less, and stillmore preferably about 1 or less; or a Shore 00 durometer of about 30 orless, more preferably of about 20 or less, and still more preferably ofabout 10 or less; or a Shore 000 durometer of 50 or less, and mostpreferably 30 or less.

In certain embodiments, the viscoelastic foam exhibits a tack measuredusing the Standard Test Method for Pressure-Sensitive Tack of AdhesivesASTM D2979-16 of at least 0.1 mJ/cm², preferably at least 0.3 mJ/cm²,and most preferably at least 0.5 mJ/cm². Thus, in various embodiments,the tack is between 0.1 and 9 mJ/cm², between 0.3 and 7 mJ/cm², andbetween 0.5 and 5 mJ/cm².

By “inherent tack” is meant that the viscoelastic foam material isitself tacky, as opposed to having a tacky material added to a surfaceof the foam after the production of the foam. In certain embodiments,the inherent tack is provided without the addition of tackifiers.

In certain embodiments, the viscoelastic foam may comprise or consist ofa foamed silicone rubber, such as a high consistency rubber (“HCR”) or aliquid silicone rubber (“LSR”). Such a viscoelastic foam may be formedfrom silicone rubber and foaming agent blended together and cured toproduce a compliant, durable human interface layer. The viscoelasticfoam may be provided as a single layer, or may be a component of alamination stack of materials positioned on all or a portion of thetissue interface portion of the appliance. In the case of a laminationstack, the viscoelastic foam preferably provides the outermost layer(and hence provides the tissue contact layer) of the lamination stack.

One substantial advantage of using foamed LSR as an interface materialover other foam materials is the inherently higher thermal conductivityof silicone versus materials such as polyurethane “memory” foams. Thismakes foamed LSR cooler on the skin. This greater thermal conductivitycan be further enhanced by adding various filler components such asSi₃N₄, Al₂O₃ and ZnO, and non-metal fillers like BN and graphite. Incertain embodiments, the filler can be vinyl endblockedpolymethylsiloxane reinforced with silicone nitride (Si₃N₄) particlesalone or in combination with silicone carbide whisker (SiCw) asdescribed in Zhou et al., J. Composite Materials 42: 173-87, 2008.Enhancement of thermal conductivity can be achieved by adding actualmetal particles, particularly copper nanowires or various compositessuch as silver coated copper or aluminum, nickel coated graphite. Inaddition, the inherent conductivity of silicone polymers can be enhancedby fabrication processes that lead to a better “lining up” of thepolymer chains in the cured material.

Thermal conductivity of silicone rubber is approximately 0.2 W/mK.Commercially available silicone rubbers with fillers such as WACKERSemicosil can provide thermal conductivities above 1 W/mK and as high as4.3 W/mK. The addition of additives such as Si₃N₄ particles can provideconductivities above 1 W/mK and as high as 1.8 W/mK. Zhou et al.,Composites Part A: Applied Science and Manufacturing 40: 830-836, 2009.In contrast, m polyurethane foams have thermal conductivity as low as0.022 W/mK and typically less than 0.060 W/mK. WO2014/105690.

In certain embodiments, the viscoelastic foam may comprise a tackifieradded during production of the foam. Tackifiers are chemical compoundsused in formulating elastomers to increase the tack, the stickiness ofthe surface of the adhesive. See, e.g., U.S. Pat. Nos. 4,073,776; and7,772,345. Tackifiers tend to have low molecular weight, and glasstransition and softening temperature above room temperature, providingthem with suitable viscoelastic properties. Tackifiers can comprise upto about 40% of total mass. Examples of tackifiers include rosins andtheir derivatives, terpenes and modified terpenes, aliphatic,cycloaliphatic and aromatic resins (C5 aliphatic resins, C9 aromaticresins, and C5/C9 aliphatic/aromatic resins), hydrogenated hydrocarbonresins, and their mixtures, terpene-phenol resins (TPR, used often withethylene-vinyl acetate adhesives)). Silicone rubber-basedpressure-sensitive adhesives may utilize special tackifiers based on“MQ” silicate resins, composed typically of a monofunctional trimethylsilane (“M”) reacted with quadrafunctional silicon tetrachloride orsilicone tetroxide (“Q”). In certain embodiments, the viscoelastic foamdoes not include a tackifier or an adhesive.

While tackifiers may find use in the present invention, in preferredembodiments the viscoelastic foam does not comprise tackifiers or anadhesive, and the tack quality is an inherent property of the elastomeritself.

In certain embodiments, the viscoelastic foam is formed using a siliconebase, a foaming agent, and a catalyst. An example of such a foamingagent is an ammonium, sodium, or potassium salt, however a variety ofcommercially available chemical foaming agents are known in the art.Typically, these foaming agents liberate a gas (e.g., N₂, CO₂) duringthe foaming process. A catalyst may be selected from the groupconsisting of an iron catalyst, a cobalt catalyst, a zinc catalyst, atitanate catalyst, a tin catalyst, a platinum catalyst, or an acidcatalyst.

While it is preferred that the entire tissue interface portion of theappliance comprise the viscoelastic foam, in certain embodiments onlyportions of the tissue interface portion comprises the viscoelasticfoam. In certain embodiments, the viscoelastic foam may be one or amultiplicity of continuous or discontinuous concentric annular rings,either abutting or having some pitch separation between them. In otherembodiments, the viscoelastic foam may be one or a multiplicity ofconnected or discontinuous spiral rings, either abutting or having somepitch separation between them.

The percentage by weight of the foaming agent additive to theelastomeric component (e.g., a silicone rubber) will preferably be 1 to10%, and more preferably 1 to 5%, and most preferably 1.5 to 3%. Invarious embodiments, the viscoelastic foamed material will be appliedonto the appliance and cured in such a manner as to cause theviscoelastic foamed material to “skin-over,” providing a smooth closedcell surface at the tissue contact surface of the viscoelastic foamedmaterial that helps to mitigate potential leakage around the interfaceseal, moisture (e.g., perspiration) absorption and/or particlecontamination (eg. skin, stubble, debris) into the foam matrix, andgrowth of product damaging microbes (e.g., bacteria, fungi, algae)either on the surface or within the foam matrix. Alternatively, thermalconductivity and breathability of the foamed interface material can beenhanced by fabrication techniques such as reducing the “skinning over”of the contact surface and/or enhancing the porosity of the foam to bemore of an open cell foam structure than a closed cell structure.However, these approaches would enhance the ability of the material toabsorb and hold water which may not be desirable from a washabilityviewpoint.

In certain embodiments, the viscoelastic foam comprises a reinforcingfiller such as silica, silica aerogel, silica xerogel, titanium dioxide,diatomaceous earth, iron oxide, aluminum oxide, zinc oxide, quartz,calcium, carbonate, magnesium oxide, carbon black, graphite, glassfibers, glass micro spheres, glass micro balloons, glass beads, carbonfibers, silicon carbide, polystyrene beads, microcrystalline cellulose,nanoparticles such as carbon nanotubes, layered silicate etc., and metalfibers.

In certain embodiments, the viscoelastic foam comprises an antimicrobialadditive with active ingredients such as a silver, silver ions, silverions encapsulated in a glass particle, silver sodium zirconiumhydrogenphosphate, 3-(Trimethoxysilyl)propyl dimethyl octadecyl ammoniumchloride, benzalkonium chloride, benzethonium chloride, chloroxylenol,polyhexamethylenebiguanide (PHMB), etc., that are metabolized by themicrobial cells to retard or prevent the growth of microbes such asbacteria, fungi, and viruses. Some of these may be supplied in the formof inorganic compounds and may comprise either micro-sized (>100 nm) ornano-sized (<100 nm) particles.

In certain embodiments, the viscoelastic foam comprises a leachresistant, non-migrating antimicrobial additive comprising a siloxanepolymer. Such materials are not metabolized by the microbial cells, andinstead creates a network of electrically charged molecules on thesurface of the viscoelastic foam matrix that ruptures the microbial cellwall of bacteria, fungi, and algae.

In certain embodiments, the sealing element may comprise a tackymaterial inherent in, or positioned on, all or a portion of the contactarea. By way of example only, the tacky material can comprise either aroom-temperature vulcanizing or a heat-curing silicone rubber. The tackymaterial may be a single layer, or may be a component of a laminationstack of materials positioned on all or a portion of the contact area.

In certain embodiments, the viscoelastic foam provides a fluidly sealedsurface.

While foaming and cure of a viscoelastic foam may take place at roomtemperature, in certain embodiments, the viscoelastic foam is cured at atemperature of at least between about 50° C. and 60° C., more preferablyat least about 120° C., still more preferably at least about 150° C.,and yet more preferably at least about 170° C.

Examples of silicone foams and processes to make them may be found, forexample, in U.S. Pat. Nos. 8,410,239; 8,173,717; 7,393,879; 6,022,904;and 5,436,274, each of which is hereby incorporated by reference in itsentirety. In certain embodiments, curing takes place at a temperaturebetween about 100° C. and about 250° C.

In certain embodiments, the viscoelastic foam has a density of 0.9 g/cm³or less, more preferably 0.8 g/cm³ or less, still more preferably 0.7g/cm³ or less, and most preferably 0.5 g/cm³ or less.

In various embodiments, the medical or cosmetic appliance may be an eyeprotection mask, a scuba mask, swim goggles, a medical appliance, abreathing mask, a negative pressure chamber configured to cover aportion of the body such as a negative-pressure wound therapy device ora continuous negative external pressure (cNEP) therapy device,headphones, ear plugs, earphones, brassieres, swimwear, or the like.

As described hereinafter, the appliance described herein may be onesuited for providing a pressure containment structure in the form of asealed chamber that is configured to administer negative, neutral orpositive pressure to a targeted therapy area on the external or internaltissue of an individual.

The term “pressure containment structure,” as used herein refers to theelements of the therapy device that contain a negative pressure,positive or neutral pressure during use. The pressure containmentstructure may comprise a rigid, semi-rigid, or flexible membrane thatdefines a dome-like chamber element, an aperture in the pressurecontainment structure through which a vacuum source may be affixed orapplied through, and a sealing element affixed to the dome-like chamberthat forms the tissue interface portion between the chamber element andthe individual.

Such a pressure containment structure may be used to create a pressuredifferential between an interior space formed by the appliance whenmated to living tissue (e.g., a location on a human), and the exterioratmospheric pressure. Preferably, the viscoelastic foam creates a sealto the tissue that maintains the pressure differential. A certain amountof leakage at the seal may be tolerated so long as the desired pressuredifferential can be achieved and maintained. Preferably, the leakage isno more than between about 0.008 ml/min and about 8 ml/min, and mostpreferably between about 0.1 ml/min and about 1.6 ml/min. In the case ofan eye mask for use in water (e.g., a SCUBA mask), the viscoelastic foamis preferably fluidly sealed to seawater such that a pressuredifferential of about 1 atm leaks no more than 10% of the internalvolume, and preferably 5% of the internal volume or less, in 10 minutes,20 minutes, or most preferably 30 minutes.

In certain embodiments, the appliance may be configured to provide anapproximately constant and evenly distributed contact pressure acrossthe entire tissue interface portion when the appliance is mated to theindividual and a therapeutic level of pressure (either positive ornegative) is applied within the appliance. In the case of a negativepressure appliance, this approximate contact pressure may range from 0.9to 1.5 times, and preferably be about 1.1 to 1.3 times, the negativepressure within the therapy device.

In certain embodiments, when the therapy device is mated to theindividual and a therapeutic level of negative pressure is appliedwithin the chamber, the approximate contact pressure applied to thetissue surface is approximately 1.2 times the negative pressure withinthe chamber. In various embodiments, a therapy device designed tomaintain a neutral or positive pressure within the chamber could also beconfigured to distribute a constant and even contact pressure.

In related aspects, the present invention relates to methods of applyingnegative pressure therapy to an individual in need thereof, comprisingmating a therapy device as described herein to the individual, andapplying a therapeutic level of negative pressure within the chamber,thereby increasing patency of the airway of the individual. Such methodscan be for treatment of sleep apnea; for treatment of snoring; fortreatment of full or partial upper airway collapse, whether during sleepor during medical procedures requiring some level of sedation; fortreatment of full or partial upper airway obstruction; for negativepressure treatment of a wound caused by, for example an injury or asurgery; etc.

The terms “external area” and “external surface” of an individual asused herein refers to a portion of the external tissue surface of theindividual. The terms “internal area” and “internal surface” of anindividual as used herein refers to a portion of the internal surface orpartially internal surface of the individual. For example, in variousembodiments, the therapy device may be configured to be applied to andseal sites of ostomies or wounds or to sealing around laryngeal tubes inthe airway. Other internal applications would include on the exterior ofimplants to cushion a mechanical stiffness mismatch between an implantand its adjoining tissue, or as all or a portion of a tissue fillermaterial such as in cheek, breast and buttocks implants. In variousembodiments, the therapy device is configured to provide optimizedfitting parameters, for example, seal, comfort and local devicecompliance throughout all points of contact. This may be achieved byminimizing the contact pressure differential from one point of contacton the tissue of a patient to another through design features of thecompliant conforming interface and design features of the sealed chamberelement of a negative pressure therapy device.

In certain embodiments, a chamber element may be affixed to a flangeelement as an integral structure, as a unitary structure, or as discretestructures. The flange element provides mechanical support for theinterface between the apparatus and the tissue of the user. As usedherein a compliant conforming interface is defined as a flexible, shearabsorbing and compressible surface capable of stretching, bending and orflexing to form an approximate air-tight seal between the chamberelement and the user.

In certain embodiments, a compliant conforming interface between thetherapy device and the individual varies in width and/or thicknessaround the circumferential dimension of the therapy device. By varyingthe conforming interface, the magnitude of forces applied to the tissuesurface of the individual can be varied from point to point around thecontinuous contact area. In this manner, the force applied to theexternal surface of the individual at any point along thecircumferential dimension of the sealing element may be made to be“constant.” In this context, the term “constant” as used herein, refersto maintaining the force within about 20%, and more preferably about10%, of the average force along the entire circumferential dimension ofthe sealing element, where the force at each point along thecircumferential dimension of the sealing element is measured at thelocation on the width dimension of the flange element at which sealingelement contacts the user.

Any and all vacuum, gas, or fluid pump types find use in the presentinvention, provided that a desired level of flow can be achieved by theselected pump. In certain embodiments, the pump may be connected to theapparatus via a hose or tube. For greatest mobility, a pump ispreferably wearable by the patient and is battery powered, and mostpreferably the air pump is configured integrally to the appliance.

In certain embodiments, a vacuum pump may be a manual squeeze bulb, ormay be electric and comprise a piezoelectric material configured toprovide an oscillatory pumping motion. It is most preferred that theoscillatory pumping motion operates at a frequency greater than 500 Hz.

In those embodiments where the pump is configured integrally to theapparatus, a sealing feature between the pump and the appliancepreferably forms an airtight seal. By way of example, a compliantsealing ring or lip seal may be provided within the opening into whichthe pump engages. The sealing feature may be provided integrally withthe chamber element, and most preferably as a unitary structure with thechamber element. Alternatively, the compliant sealing ring and thechamber element are discrete structures

In certain embodiments of a negative pressure device, the chamberelement comprises one or more apertures creating vent elements thatprovide a controlled airflow into the chamber when the therapy device ismated to the individual and a therapeutic level of negative pressure isapplied. The apertures, located distal to the intake of a pump elementprovide a flow of air through the chamber that may primarily assist tofacilitate hysteretic control of a vacuum therapy range, and secondarilyassist the exchange of air within the interior of the chamber. As usedherein, hysteretic control is defined as the reaction of the controlsystem within a range to change the flow rate of the vacuum pump to aperceived change in absolute barometric pressure within the chamberelement of the negative pressure device. The range provides twopoints—an “on rise” point at which the pump is energized, and an “onfall” point at which the pump is turned off. The aperture(s) providingan airflow that is preferably between about 10 mL/min and about 300mL/min, and most preferably between about 20 mL/min and about 150mL/min, and still more preferably between about 40 mL/min and about 100mL/min.

In some embodiments, the vent element can comprise an aperture and afilter element within the aperture, wherein the filter element comprisesa pore size of about 1.0 μm or less, such as a pore size of about 0.7μm. The filter element can be configured as a replaceable element andthe size adjusted to provide an airflow preferably between about 10mL/min and about 300 mL/min, and most preferably between about 20 mL/minand about 150 mL/min, and still more preferably between about 40 mL/minand about 100 mL/min.

In yet another embodiment, the vent element can comprise one or aplurality of holes distal to the intake of the pump element and of asufficiently small size to exclude debris from entering the chamber. Thenumber of holes and diameter of the hole size further enables thedesired airflow of preferably between about 10 mL/min and about 300mL/min, and most preferably between about 20 mL/min and about 150mL/min, and still more preferably between about 40 mL/min and about 100mL/min, wherein the hole size is between about 25 um to about 200 um andmore preferably an airflow of about 40 mL/min with a hole size betweenabout 73 microns to about 83 microns

Alternatively, the level of airflow can vary. In certain embodiments,the level of airflow tied to the therapeutic level of vacuum; that is, ahigher level of vacuum can be accompanied by a higher level of airflowdue to the differential in pressure between the atmospheric side of thevent elements and the interior of the chamber. In certain embodiments,the vacuum source may be used in a variable manner to maintain thetherapeutic level of vacuum within a specified range rather than asingle value, and the level of airflow can vary in concert with thelevel of vacuum.

In related aspects, the present invention relates to methods of applyingnegative, positive or neutral pressure therapy to an individual in needthereof, comprising mating a therapy device as described herein to theindividual and applying a desired level of pressure within the chamber.In the case of a cNEP (continuous negative external pressure) airwaysupport device, the therapy devices may increase patency of the airwayof the individual. Such methods can be for treatment of sleep apnea; fortreatment of snoring; for treatment of full or partial upper airwaycollapse, whether during sleep or during medical treatment where full orpartial sedation is administered; for treatment of full or partial upperairway obstruction; for negative pressure treatment of a wound causedby, for example an injury or a surgery; etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative drawing of a cross-section of an open cavityskinned foamed elastomer 100, comprising a viscoelastic foamed tissueinterface surfaces 110, a non-contacting substrate interface surface 120and one or more gas pockets within the foamed elastomer 130.

FIG. 2 is an illustrative drawing of a cNEP airway support device 140showing a cross-hatched area representing the tissue interface surfacefully covered with a foamed elastomer 100.

FIG. 3 is an illustrative drawing of a cNEP airway support device 140showing a cross-hatched area representing the tissue interface surfacepartially covered with a foamed elastomer 100 such that the foamedelastomer forms a predominant portion of the skin contacting area of thedevice.

FIG. 4 is an illustrative drawing of a cNEP airway support device 140with uninterrupted concentric beads 150 of foamed elastomer contiguouslypositioned at a fixed pitch across the width of the viscoelastic foamedtissue interface surface 110

FIG. 5 is an illustrative drawing of the rear surfaces of a partial facemask 140, comprising a viscoelastic foamed tissue interface 110, anaperture for an air pump 115, the approximate location of the nosebridge 143, the approximate location of the cheek bone 147 andapproximate location of the chin bone 149.

FIG. 6 is an illustrative drawing of the rear surfaces of a full facemask 150 comprising an outer perimeter face sealing surface 153, a faceshield 125, a partial face mask 140 interior to the outer perimeter facesealing surface 153, the approximate location of a nose bridge 143, theapproximate lection of the cheek bone contacting surface 147, (theapproximate location of the chin bone contacting surface 149 beingobscured by the lower portion of the outer perimeter face sealingsurface 153).

FIG. 7 is a rear view of a nasal cushion 160 comprising at the nasalcups and outer tissue contact surfaces, viscoelastic foamed tissueinterface surfaces 110.

DETAILED DESCRIPTION OF THE INVENTION

The present invention and the various features and advantageous detailsthereof are explained more fully with reference to the non-limitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. It should be noted that thefeatures illustrated in the drawings are not necessarily drawn to scale.Descriptions of well-known components and processing techniques areomitted so as to not unnecessarily obscure the present invention. Theexamples used herein are intended merely to facilitate an understandingof ways in which the invention may be practiced and to further enablethose of skill in the art to practice the invention. Accordingly, theexamples should not be construed as limiting the scope of the invention.In the drawings, like reference numerals designate corresponding partsthroughout the several views.

In the present invention, an appliance is configured to contact livingtissue or similar surfaces comprising a viscoelastic foam. Ideally, thecontact surface of the appliance provides an appropriate balance betweenviscoelastic properties that enable the material to adapt to anatomicaldifferences between individuals as well as changes that may occur as aresult of movement by a given individual—the former implying a lowviscous modulus enabling the material to flow/adapt, the latter implyinga low elastic modulus enabling the material to recover. Of particularnote in various embodiments are a very low (tissue-like) durometerextending into the Shore 000 scale range, an inherent tackiness, aclosed-cell surface, enhanced cleanability, and enhanced durability.

In addition, the contact surface ideally comprises a level of tackinessto prevent an appliance from sliding on the living tissue that wouldotherwise result in skin abrasion or chafing or internal implantmovement, and to help maintain an air-tight seal between the applianceand the living tissue in both static and dynamic conditions. The contactsurface should be tissue-like in stiffness, extremely low in skinsensitivity or allergic reaction, and be reasonably impervious tomicrobial growth. Finally, if used in a repeated-use (e.g., externalapplication such as for skin contact) application, cleaning must befacilitated such that, not only is the interface material not degraded,but dirt, grime, stubble, make-up, and/or perspiration is removable withsurface tackiness maintained.

In achieving the object of the invention—i.e. a compliant interfacebetween an appliance and living tissue—it has been determined thatreducing the durometer of the elastomeric foam will result in acorresponding reduction in viscoelastic moduli (measured by storage andloss moduli). An increase in foaming agent concentration will have theresult of reducing viscoelastic moduli albeit not as strong an influenceas durometer.

It has also been determined herein that foaming of an elastomericmaterial may be used to achieve surface tackiness without the additionof tackifiers. A low concentration (e.g., less than 5% and preferablyless than 3%) of foaming agent results in a compliant structure that,when loaded, has higher surface tackiness than its non-foamed variant.

Additionally, to enhance cleanability, the outer surface of theelastomeric foamed material may be “skinned-over” by means of how it isformed during fabrication, thereby closing the otherwise open-cellstructure of the surface and replacing it with an integral closed,continuous surface that resists contamination.

The following are preferred viscoelastic properties of a viscoelasticfoam for use in the present invention:

More Most Preferably Preferably Preferably 1 Shore A Durometerw/1.5-3.0% Foaming Agent Elastic Modulus (kPa)  0.3-27.8  0.8-23.5 1.2-19.2 Viscous Modulus (kPa) 0.5-5.4 0.6-4.6 0.7-3.9 5 Shore ADurometer w/1.5-3.0% Foaming Agent Elastic Modulus (kPa)  0.3-19.0 0.9-16.8  1.4-14.6 Viscous Modulus (kPa) 0.4-3.6 0.5-3.3 0.6-2.9 1Shore A Durometer + 1.5% Foaming Agent Elastic Modulus (kPa)  1.4-27.8 1.7-23.5  2.0-19.2 Viscous Modulus (kPa) 0.8-5.4 0.9-4.6 1.0-3.9 1Shore A Durometer + 3.0% Foaming Agent Elastic Modulus (kPa) 0.3-8.10.8-7.6 1.2-7.0 Viscous Modulus (kPa) 0.5-2.4 0.6-2.2 0.7-2.0 5 Shore ADurometer + 1.5% Foaming Agent Elastic Modulus (kPa)  0.3-19.0  0.9-16.8 1.5-14.6 Viscous Modulus (kPa) 0.6-3.6 0.7-3.3 0.8-2.9 5 Shore ADurometer + 3.0% Foaming Agent Elastic Modulus (kPa)  0.7-14.2  1.0-12.5 1.4-10.7 Viscous Modulus (kPa) 0.4-3.5 0.5-3.1 0.6-2.6

In certain embodiments, the viscoelastic foam defines one or moresurfaces of a negative, positive or neutral pressure therapy device thatcontacts living tissue or similar surfaces and is designed to maximizecomfort and seal efficiency, ultimately optimizing device efficacy anduser compliance. In certain embodiments, a non-tissue contacting portion(non-contacting portion) of the appliance provides support for theviscoelastic foam element and an interface between the appliance and theviscoelastic foam that contacts the living tissue. In certainembodiments, the viscoelastic foam may be applied to a negative pressurechamber configured to cover a portion of the body as described below foruse in opening the upper airway of an individual when placed upon theanterior neck region of a subject over a surface corresponding toapproximately the upper airway of the subject.

This exemplary application of the technology is not meant to belimiting. The viscoelastic foam may further find use as one or morecontact surfaces of additional appliances meant for limited or prolongedcontact with or treatment of tissue sites, including but not limited tomedical appliances for example, infusion sites or sites of living tissuecontact for biometric data gathering for example, ECG and EKGelectrodes, continuous glucose monitoring (CGM) systems, tracheal tubes,catheters, medical balloons, partial face masks (FIG. 5) wherein FIG. 5shows the rear surfaces of a partial face mask 140, comprising a foamedelastomeric tissue interface 110, an aperture for an air pump 115, theapproximate location of the nose bridge 143, the approximate location ofthe cheek bone 147 and approximate location of the chin bone 149, fullface masks (FIG. 6), wherein FIG. 6 shows the rear surfaces of a fullface mask 150 comprising an outer perimeter face sealing surface 153, aface shield 125, a partial face mask 140 interior to the outer perimeterface sealing surface 153, the approximate location of a nose bridge 143,the approximate location of the cheek bone contacting surface 147, (theapproximate location of the chin bone contacting surface 149 beingobscured by the lower portion of the outer perimeter face sealingsurface 153). Wherein the outer perimeter face sealing surface 153 andpartial face mask 140 sealing surface can be, fully or partially coveredwith the foamed elastomeric material 110.

The viscoelastic foam may further find use as one or more contactsurfaces of additional appliances meant for limited or prolonged contactwith or treatment of tissue sites, including but not limited to eyeprotection masks, colostomy bags, ear plugs, ear phones, head phones,goggles, sporting equipment, brassieres and so on. The viscoelastic foamprovides for compliance in all directions including compression andsheer properties that closely mimic the living tissue it contacts for atissue friendly interface. Further, the viscoelastic foam element isdurable, abrasion resistant, shear absorbing, compressible, conformable,comfortable and washable. The viscoelastic foam may also find use as thetissue interface of a scuba or like mask wherein the viscoelastic foamis fluidly sealed to liquid such that at a pressure of about 1 atm forat least 10 minutes no more than 10% of the mask fills with liquid,where the liquid may be fresh water, sea water, oil or any substancethat flows freely but is of a constant volume.

In certain embodiments, the viscoelastic foam element comprises density,durometer and probe tack properties as follows:

Viscoelastic foam Material Fabrication Range Density Durometer TackProcess Preference (g/cm³) (Shore) (mJ/cm²) Open Cavity Preferably0.1-0.8 <10 (00) 0.1-9 More 0.2-0.7 <50 (000) 0.3-7 Preferably Most0.3-0.5 5-30 (000) 0.5-5 Preferably Closed Cavity Preferably 0.3-0.9 <10(00) 0.1-9 More 0.5-0.8 <80 (000) 0.3-7 Preferably Most 0.6-0.7 20-40(000) 0.5-5 Preferably

Wherein the (EFMFP) is the Elastomeric Foam Material Fabrication Processand is defined by the manner in which the viscoelastic foam is cured.EFMFP is categorized by either an “Open Cavity” process or a “ClosedCavity” process. As used herein, an open cavity viscoelastic foammaterial fabrication process is defined by the application of aviscoelastic foam element upon a substrate for curing outside a moldingfeature. In open cavity processes, the viscoelastic foam may simply beapplied to the substrate and allowed to cure in any desired manner forexample at room temperature, under the application of heat, UV light ora combination thereof for example. As used herein, a closed cavityviscoelastic foam material fabrication process is defined by theapplication or injection of a viscoelastic foam element into an enclosedmold containing a substrate and generally under vacuum for curing theviscoelastic foam element to the substrate within the mold, for examplethe process of overmolding. Cure in these processes can similarly beachieved in any appropriate fashion, for example through the addition ofcatalysts, heat, UV light or a combination thereof.

Wherein density is defined as the degree of consistency measured by thequantity of mass of a substance per unit volume, for example, grams percubic centimeter (g/cm³). In open cavity viscoelastic foam materialfabrication processes, the density of the viscoelastic foamed materialis preferably between 0.1-0.8 g/cm³, more preferably between 0.2-0.7g/cm³ and most preferably between 0.3-0.5 g/cm³. In closed cavityviscoelastic foamed material fabrication processes, the density of theviscoelastic foamed material is preferably between 0.4-0.9 g/cm³, morepreferably between 0.5-0.8 g/cm³ and most preferably between 0.6-0.7g/cm³.

Wherein durometer is defined as a measure of hardness measured by theASTM D2240 scales. In open cavity viscoelastic foam material fabricationprocess, the durometer is preferably less than about 10 Shore 00, morepreferably less than about 50 Shore 000, and more preferably betweenabout 5 and 30 Shore 000. In closed cavity viscoelastic foam materialfabrication processes, the durometer is preferably less than about 10Shore 00, more preferably less than about 80 Shore 000 and mostpreferably between about 20-40 Shore 000.

Wherein the Probe Tack is defined as the force required to separate anadhesive-like element and the adhered probe as measured by the ASTMD2979 Standard Test Method for Pressure-Sensitive Tack of Adhesives. Inopen cavity viscoelastic foam material fabrication process, the ProbeTack is preferably less than about 9 mJ/cm², more preferably less than 7mJ/cm², and more preferably between about 5 mJ/cm². In close cavityviscoelastic foam material fabrication processes, the Probe Tack ispreferably less than 9 mJ/cm², more preferably less than about 7 mJ/cm²and most preferably between about 5 mJ/cm².

In certain embodiments, the viscoelastic foamed material element is afoamed silicone rubber material that is produced by blending acombination of silicone rubber and a foaming agent, resulting in a foamcellular structure that increases in thickness upon curing preferablybetween 50 to 300%, and more preferably 75 to 250%, and most preferably100 to 200%.

In certain embodiments, the compliant conforming interface comprises aviscoelastic foamed material layer that is preferably in the thicknessrange of 0.030″ to 0.375″, or more preferably 0.050″ to 0.250″, or mostpreferably 0.075″ to 0.150″.

Foaming agents are used for producing silicone foams in room temperatureor heat-curable silicone elastomer systems. Foamed silicone rubbermaterials are designed to be conformable. Catalyst addition (e.g ironcatalyst, a cobalt catalyst, a zinc catalyst, a titanate catalyst, a tincatalyst, a platinum catalyst, or an acid catalyst) rapidly yields asilicone rubber foam at room temperature. A foam cellular structure maybe created by the release of gases during the curing process. Foams canalso be created through the use of certain additives such as ammoniumbicarbonate. Such an additive can create a cellular foam from a highconsistency rubber (HCR) or a liquid silicone rubber (LSR) via theapplication of heat.

In certain embodiments, the viscoelastic foam may be processed topromote a higher density open or closed-cell matrix on the surface thanis found through the body of the foam. Sheet forming, for example,produces a higher density, skinned-over layer on the surface exposed toopen atmosphere than that produced on the surface coated onto itscontinuous polymer sheet film carrier. Such a higher density matrix maybe desirable to mitigate moisture absorption, particle or moisturecontamination, and/or microbial growth. Additionally, cleaning isfacilitated and has a less deleterious effect where the surface is moreimpervious.

In certain embodiments, the viscoelastic foam may be coated with anadditional thin, low durometer skinned-over layer to produce aviscoelastic foam that is more impervious fluid ingress and lesssusceptible to contamination or microbial growth. The skinned-over layeron top of the viscoelastic foam produces a dual durometer structureoverall, but the overall durometer is overwhelmingly dominated by theviscoelastic foam when the ratio of it to the skinned-over layer isgreater than 10:1.

In certain embodiments, either the silicone rubber component of theviscoelastic foam, or the skinned-over layer, or both are selected fromamong the medical-grade soft skin adhesive (SSA) family of siliconescommon for use in wound care therapy. SSA silicones have the advantageof atraumatic skin removal, no skin stripping, and no painful skin orhair pulling. Another advantage is that SSA's, unlike alternatives, havea low viscous component that limits their flow and consequently theirreadiness to absorb materials at the surface of the skin such as stratumcorneum cells and lipids. The adhesive surface of SSA's remainsrelatively clean and can be removed, reused and cleaned repeatedlywithout diminishing its integrity.

A high consistency rubber consists of a high molecular weight siliconepolymer, optionally combined with a filler such as silica, to produce amaterial that can be molded, extruded, or calendared into a usefulend-product. Liquid silicone rubbers (LSR), like HCRs, may be reinforcedwith silica, but typically use lower molecular weight polymers. LSRs areoften pumped with an injection-molding machine and cured to form amolded part.

In certain embodiments, the viscoelastic foam may further comprise areinforcing filler wherein the addition of a reinforcing filler cansignificantly improve the elastomeric mechanical properties of theviscoelastic foam such as stiffness, tensile strength, tear-strength andflex fatigue for example. Reinforcing fillers may be selected from agroup containing for example an acidic filler such as fumed silica,silica, silica aerogel, silica xerogel, titanium dioxide, diatomaceousearth, iron oxide, aluminum oxide, zinc oxide, quartz, calcium,carbonate, magnesium oxide, carbon black, graphite, glass fibers, glassmicro spheres, glass micro balloons, glass beads, carbon fibers, siliconcarbide, polystyrene beads, and metal fibers.

In certain embodiments, the tissue interface portion comprises asilicone rubber material that is preferably an HCR and more preferablyan LSR material, in combination or in part. The durometer of thesilicone rubber is preferably in the range of approximately Shore Adurometer of 1 to 20, and more preferably approximately Shore Adurometer of 1 to 10. The silicone rubbers may further be foamedcreating a three-dimensional network of hydrophobic polymer chains thatcan be crosslinked either physically or chemically. Due to the foamedLSR material's significant gas content, foamed LSRs can closely resemblenatural soft tissue. Foamed properties can be achieved through theaddition of a foaming agent added to the silicon rubber material, forexample an ammonium bicarbonate dispersed in a vinyldimethyl-terminatedpolydimethylsiloxane polymer. In these examples, the ratio of foamingagent to silicone rubber by weight is preferably in the range ofapproximately 0.1% to 10%, and more preferably approximately 0.5% to 5%,and most preferably approximately 1.5% to 3%. Additional agents employedin the formation of foamed LSR may include, but are not limited to,platinum catalysts and organic tin compound catalysts.

In certain embodiments, the compliant conforming interface elementcomprises a viscoelastic foamed material with a tissue interface thathas a surface tension sufficiently high so as to mitigate or eliminatesliding between the patient tissue and the compliant conforminginterface element. Tackiness of the tissue interface further contributesto accommodating a broader cross-section of anatomical variation andcreating the necessary interface seal.

Further desired attributes or aspects of the device can be definedthrough additional material characteristics including but not limitedto, specific gravity, tensile strength, elongation, tensile modulus,tear strength, durometer, and Probe Tack, for example.

Wherein specific gravity is defined as the ratio of the density of asubstance to the density of a reference substance, for example the ratioof an elastomeric material to the density of water. In embodiments ofthe device, the specific gravity of the viscoelastic foamed material isbetween about 0.49 g/cm to about 0.72 g/cm.

Tensile properties (as measured using ASTM D412, for example) can obtainvalues for tensile strength, elongation and tensile modulus for example.

Wherein tensile strength is defined as the capacity of a material towithstand elongation loads, whereby a tensile strength (ultimate tensilestrength) is measure by the maximum stress that a material willwithstand while being stretched before fracture. In embodiments of theinvention the tensile strength of the viscoelastic foamed material ispreferably between about 31 psi to about 114 psi and more preferablybetween about 31 psi and about 62 psi.

Wherein elongation is defined as the increase in the length of theviscoelastic foamed material measured after fracture and expressed as apercentage of the original gauge length. Wherein gauge length is definedas the distance along the specimen upon which elongation calculationsare made. In embodiments of the invention the elongation of theviscoelastic foamed material is between about 438% and about 817% andmore preferably between about 438% and about 747%.

Wherein tensile modulus is defined as a measure of stiffness definingthe relationship between stress and strain. In embodiments of theinvention the tensile modulus of the viscoelastic foamed material isbetween about 5 MPa and about 10 MPa and preferably between about 6 MPaand about 7 MPa.

Wherein tear strength (as measured using ASTM D624, for example)measures the force per unit thickness (pounds per inch Ppi) required torupture or start a tear through a sample. In aspects of the invention,the viscoelastic foamed material has a tear strength between about 8 Ppiand about 32 Ppi and more preferably between about 9 Ppi and about 14Ppi.

In aspects of the invention further attributes of the viscoelasticfoamed material may include tack properties that are maintained overtime for example, times beyond curing that include storage, usage and orwashing. In certain embodiments the probe tack values of theviscoelastic foamed material as measured by the ASTM D2979 Standard TestMethod for Pressure Sensitive Tack of Adhesives using a Polyken Probetack PT-1000 instruments is maintained between about 0.43 mJ/cm² andabout 2.52 mJ/cm² for up to a week or more of curing with a maintenanceof probe tack of about 65% or more at a time period of about 4 weeks orlonger, preferably a maintenance of probe tack of about 73% or more fora period of about 4 weeks or longer and most preferably a maintenance ofprobe tack of about 83% or more.

In certain embodiments, an antimicrobial composition is added to theviscoelastic foam element. Antibacterial, antifungal, and antiviralproperties may be conveyed in any appropriate matter for example theaddition of silver salts in the form of silver sulfates, silvercitrates, silver acetates, silver carbonates, silver lactates and silverphosphates, for example. Additionally, zeolites containing approximately15% by weight of silver ion may also be used. Other suitable materials(e.g., polyhexamethylenebiguanide) are known in the art. Bacteriostatic,fungistatic, and algistatic properties may alternatively be conveyed forexample by the addition of siloxane polymers formulated into coatings inpowder, solvent, or aqueous forms, or compounded in powder form togetherwith the uncured viscoelastic foam polymer.

In certain embodiments, the compliant conforming interface elementcomprises a viscoelastic foamed material that is preferably affixedmechanically, or more preferably bonded by means of an interposingadhesive layer, or most preferably dispensed and cure-bonded directlywithout any mechanical means or additional adhesives—onto a tissueinterface portion of an appliance to form a leak-free tissue interface.In certain embodiments, Overmolding may be employed to providemechanical features on the appliance for attachment and retention of thefoam.

In certain embodiments, the compliant conforming interface elementcomprises a viscoelastic foamed material that is sheet-formed, cured,and subsequently form-cut and either affixed mechanically, or adhesivebonded onto the tissue interface portion of an appliance using aninterposing adhesive layer—RTV (room temperature vulcanizing) siliconerubber for example—to form a leak-free tissue interface.

In certain embodiments, the compliant conforming interface elementcomprises a multilayer construction of foamed silicone rubber materialthat is sheet-formed and cured, that may be coated with a thin,unvulcanized milled or calendared HCR material which latter materialserves as an adhesion layer that is heat-bonded onto the tissueinterface portion of an appliance to form a leak-free interface.

In certain embodiments, the compliant conforming interface elementcomprises a viscoelastic foamed material that may be laminated with athin adhesive film—silicone pressure sensitive adhesive film forexample—which latter material serves as an adhesion layer that ispressure-bonded onto the tissue interface portion of an appliance toform a leak-free interface.

In certain embodiments, the compliant conforming interface elementcomprises a viscoelastic foamed material that may be over-moldeddirectly onto the flange element of the collar and cured to form aleak-free tissue interface (FIG. 2, 110). As used herein, over-moldingis the process of adding material to an already molded shape creating afinal product that is partially or fully covered by the subsequentmaterial and is slightly larger than, or capping the edges of theoriginal part that represent the skin contact surface.

In certain embodiments, the present invention comprises a viscoelasticfoamed material that is continuously dispensed across the width of thenon-contact surface 120 of an appliance wherein the width of the foamedsilicone rubber is either constant or varying across the surface of thesubstrate of the appliance and cured to form a leak-free tissueinterface. As seen in FIG. 2 showing an illustrative drawing of a cNEPairway support device 140 wherein the a cross-hatched area representsthe tissue interface surface partially covered with a foamed elastomer100

In certain embodiments, a viscoelastic foamed material is continuouslydispensed and cured in one or more discrete concentric annular ringsand/or ribbons corresponding with the shape of the tissue interfaceportion of an appliance (FIG. 4, 150). Wherein an annular ring isdefined as a pattern bounded by and containing the area between twoconcentric circles or shapes. These discrete concentric annular rings orribbons may be of the same or varying thickness and or same or varyingwidth or a combination thereof on the non-contacting portion of theappliance. Said rings or ribbons may preferably be dispensed to includepitch spacing between them so as to be independent and free-standingupon heat curing, or more preferably dispensed with sufficiently narrowpitch spacing between them such that the rings and/or ribbons expand andknit together upon heat curing to form a leak-free tissue interface. Asused herein, knit together is defined as the contact or flowing togetherof the outer edges of one or more of the rings or ribbons forming auniform feature and or a feature of peaks and valleys of the rings orribbons. Wherein the peaks are defined as thicker regions of the ringsor ribbons as compared to the valleys which are defined as thinnerregions of the rings of ribbons. As used herein, pitch separation isdefined as the dimensional distance between two recurring features forexample the dimensional separation between the centerlines of concentricannular rings of viscoelastic foamed material.

In certain embodiments, the tissue interface portion comprises aviscoelastic foamed material that is continuously dispensed and cured ina continuous spiral ring and/or ribbon corresponding with the shape ofthe tissue interface portion of the appliance. Said continuous spiralring or ribbon may preferably be dispensed to include pitch spacingbetween the successive dispensed rings/ribbons so as to be independentand free-standing upon heat curing, or more preferably dispensed withsufficiently narrow pitch spacing between them such that the successiverings and/or ribbons expand and knit together upon heat curing to form aleak-free tissue interface.

In certain embodiments, the tissue interface portion comprises aviscoelastic foamed material that is dispensed in a dot matrix patternfor example with sufficiently narrow pitch spacing between the dispensedelements such that they expand and knit together upon heat curing toform a continuous leak-free tissue interface.

In certain embodiments, the viscoelastic foam material of the presentinvention will be sufficiently supple and conformable to facilitate somepre-existing or overnight growth of stubble without compromising thenecessary therapeutic interface seal. In a viscoelastic foamed material,the range of suitable silicone rubber durometer and foaming agentconcentration is preferably in the range of 1 to 10 Shore A and 1.5 to3% respectively. The resultant viscoelastic foam having a finaldurometer of less than 10 Shore 00 and more preferably a final durometerrange of approximately 1 to 40 Shore 000.

In certain embodiments, the compliant conforming interface elementcomprises a foamed silicone rubber material whose foam cellularstructure is preferably produced by a subtractive process wherein saltof a given particle size and concentration is uniformly blended with anLSR formulation and subsequently washed-out (i.e. dissolved orsubtracted) leaving behind a cellular structure, and more preferablyproduced by a gas expansion process wherein a foaming agent of a givenparticle size and concentration is uniformly blended with an LSRformulation and subsequently expanded by the application of heat toresult in a cellular structure.

Optionally, an adhesive layer or gel is located on the surface of thecompliant conforming interface element that makes contact with the user.Silicone gels for example are designed to be soft and conformable. Theyachieve their gel-like consistency by having less crosslinking than istypical of elastomers and are generally not silica-reinforced. Uncuredgels are easily pourable and can be mixed by hand and molded intofinished parts. An adhesive or gel layer aims to reduce movement of thedevice on the wearer as well as enhance the seal and cushioning on thewearer. These elements are configured to maintain an approximate uniformcontact pressure with minimized pressure variations along the tissue ofan individual through all points of contact of the therapy device on apatient. By “minimized pressure variation” means a pressure at any pointbetween the contact surface of the sealing element and the patient'stissue varies by no more than about 20%, and preferably no more thanabout 10% or about 5%, from the average pressure across the entirecontact surface. The outer contact surface, as used herein, is thesurface of the sealing element of the therapy device that makes contactwith the tissue of the individual forming the contact and sealing tissueinterface portion of the appliance.

In certain embodiments, a therapy device comprised of a chamber and asealing element is configured to be the contacting surface between thechamber and the user described herein is configured to provide forregional load equalization over the interface between a negativepressure therapy device and the three-dimensional varying tissue surfaceof the user so as to maintain a near uniform contact pressure over thisnon-uniform surface.

In particular, the therapy device referred to herein relates but is notlimited to an external therapy appliance for relieving upper airwayobstruction. U.S. patent application Ser. Nos. 12/002,515, 12/993,311and 13/881,836 which are hereby incorporated by reference in theirentirety including all tables, figures and claims, describes a therapyappliance for relieving airway obstruction. Increasing the patency ofthe upper airway of an individual alleviates conditions such a snoring,sleep apnea, full or partial upper airway collapse whether during sleepor during medical procedures where sedation has been administered. Asdescribed therein, a device is configured to fit under the chin of auser at an external location corresponding to the soft tissues overlyingthe upper respiratory passages of the neck.

In various embodiments, the viscoelastic foamed material characteristicsmay include an ability to maintain desired material characteristics at arange of varied temperatures. These characteristics further enable theability of the tissue contacting surface of the viscoelastic foamedmaterial of a device to conform to a moving and flexing living tissueinterface surface, tissue-like interfacing surfaces as well as anon-tissue contacting surface that may or may not be a moving or flexingsurface, for example surfaces of a rigid or flexible wearable applianceor features thereof.

As described herein the viscoelastic foamed material may find use as aninterface between living tissue surfaces, tissue-like surfaces and ornon-tissue surfaces of a rigid or flexible wearable appliance orfeatures thereof. The viscoelastic foamed material providing acompliant, comfortable fitting interface enabling and encouraging usagefor periodic or prolonged usage of devices. Although the duration of usemay depend on application, duration of therapy needed and protectionetc., the viscoelastic foamed material can alleviate negativelimitations of fit and feel of appliances not including the viscoelasticfoamed material.

Appliances benefiting from the viscoelastic foamed material interfacemay be prescribed, and/or required by a Chemical Hygiene Plan (CHP) forexample, and may include but are not limited to interfaces betweenmedical and or therapy devices and a user (prosthetic devices, positiveor negative pressure therapy devices, CPAP appliances, cNEP appliances,laryngeal mask airway (LMA's), nasal prongs, nasal pillows (FIG. 7),airway insertion devices, catheter protection/sealing systems and soon). Further applications may include but are not limited to interfacesbetween civilian or military Personal Protective Equipment (PPE) and auser. Applications can further include respiratory protection, particleand or gas mask interface surfaces and/or interface surfaces ofprotective clothing or protective barriers used to seal regions of anappliance and tissue, tissue-like and or non-tissue surfaces.Applications can be found in Level A, Level B, Level C and/or Level D,OSHA-rated protection including but not limited to, pressure demand,self-contained breathing apparatus (SCBA), gloves, foot and eyeprotection, earplugs, ear muffs (for noise dampening and protection),knee, elbow and/or wrist pads, helmets, hats, full or partial-facedpositive or negative pressure respirators and or full body suits,theatrical appliances including masks, wigs, ears, noses, foreheadprosthetics, cheeks, chins, brow appliances and small makeup FX piecesand so on.

In various embodiments the foamed elastic material may be in the form ofan injectable or pre-formed material to fill wrinkles, furrows, acnescars or to add volume to lips and cheeks, for example, or breasts andbuttocks in a larger structure. Silicone rubber is less expensive thanfillers like collagen and Restylane, easy to work with and side effectsoccur in less than 1% of patients. Further, fillers such as collagen andRestylane are absorbed by the body within about 6 months making siliconea more permanent option. Uncontrolled or free silicone is generally notwell tolerated in the body making a cured coating, curing injection orpre-cured implant preferable. As used herein, a cured coating is definedas a layer of the viscoelastic foamed material that is applied to adesired surface in an un-cured state (possibly liquid or gel) and curedto its final viscoelastic foamed form via heat, UV or a chemicalcatalyst for example. As used herein a curing injection is defined asthe injection of the uncured viscoelastic foamed material and a catalystinto a desired location wherein the viscoelastic foamed material cancure to its final viscoelastic foamed form where placed throughinjection. As used herein a pre-cured implant is defined as aviscoelastic foamed material that is cured to a desired shape andutilized or implanted at a desired location.

In certain embodiments the viscoelastic foamed material may find use asa coating for catheters, guidewires, stents, grafts and or stent-graftsby protecting vessel walls during insertion, lowering deployment orextraction forces of the devices as well as providing a tissue-likeinterface between all, part or selected portions of the devices.Further, the viscoelastic foamed material can be mixed withanti-proliferative agents to reduce the restenosis to improve clinicaloutcomes. As used herein, deployment force is defined as the outwardforce exerted by a device such as a stent as it deploys from its initialdiameter to its working diameter, as measured within a glass tube havingthe correct internal diameter. Suitable testing machines (WL2100;Withlab, Gunpo, Gyeonggi-do, Korea) for measuring deployment force areknown in the art.

In further embodiments the viscoelastic foamed material may find use asa ureteral stent or a coating for ureteral stents by protecting theureteral wall, kidney, bladder and urethra providing a tissue-likestructure and or interface between all, part or selected portions of thestent.

In certain embodiments, the viscoelastic foamed material may find use inrepair of non-ruptured aortoiliac aneurysm (AAA) or conditions of thelike wherein, for example, a stent graft, comprising a stent portion foranchoring to the aortic wall and a graft portion, comprising a networkof channels is used to repair an aneurysm. The stent graft is deliveredwithin a catheter in a compressed state and when released from thecompressed state the stent engages the vessel wall and the graft isexpanded to direct blood flow. The aneurysm is then sealed via fillingthe space between the graft and vessel wall by injecting the fillingmaterial either directly or by inflating sealing chambers, endo-bags andother support-type structures (ring-shaped ribs for example) usingappropriate filling material, for example the viscoelastic foamedmaterial. The components of the viscoelastic foamed material is mixed tobegin the cross-linking to form the fill of viscoelastic foamedmaterial. Mixing of the components may occur prior to filling the graftor mixed within the graft during fill. The viscosity remains low aftermixing to aid in fill and then thickens, changing from liquid to form asoft, compliant, yet firm solid. The mixed viscoelastic foamed materialmay further comprise a contrasting material to aid the physician tovisualize appropriate deployment wherein the material is injected intothe inflatable sealing chambers of a graft.

In certain embodiments the viscoelastic foamed material may be used asan interface between living tissue and a prosthetic device. Theviscoelastic foamed material may satisfy critical features necessary forsupporting the structure of living tissue, living tissue maintenance,living tissue repair as well as provide a more favorable functionalrelationship between a prosthetic device and the living tissue. Theviscoelastic foamed material can be designed to reproduce the structuralhierarchy of complex tissues by varying physical properties of theviscoelastic foamed material to more favorably interface between all orpart of the living tissue and a prosthetic. The viscoelastic foamedmaterial may be used to form a layer between the living tissue and aprosthetic in a uniform or varying thickness and in a uniform or varyingdurometer to accommodate variations in the living tissue and theprosthetic. Further, the probe tack of the viscoelastic foamed materialmay favorably bias adhesion of the viscoelastic foamed material to theliving tissue and favorably bias adhesion of the viscoelastic foamedmaterial to the prosthetic providing a more favorable interface betweenthe prosthetic and the user. Further, air pockets inherent to theviscoelastic foamed material may further provide favorable adhesionbetween the prosthetic and the user during instance of water saturationeither by perspiration or other instance of water contact by capturingand or removing moisture between the living tissue and the viscoelasticfoamed material while substantially maintaining the probe tack of theviscoelastic foamed material.

For purposes of the patent application, the term “about” refers to+/−10% of any given value.

The negative pressure therapy device of the present invention comprisesa flexible membrane element, an aperture through the flexible membraneelement and a compliant tissue interface portion positioned along theedge or face of the flexible membrane element along the circumferentialdimension of the tissue interface portion to form an airtight junctionbetween the tissue interface portion and the flexible membrane element.The junction between the non-contacting portion of the tissue interfaceportion and the chamber element is referred to herein as the “root” ofthe junction. As used herein a compliant element is defined as a onethat is flexible, for example the compliant tissue interface portion,though in the approximate shape of the contact surface a target therapyarea is flexible as to accommodate variation.

As used herein, the term “circumferential dimension” refers to acontinuous location along the width of the tissue interface portion andin some cases, for example where the chamber element makes continuouscontact with the non-contacting portion of the appliance. As usedherein, the “root” is the location at which the chamber element contactsthe non-contacting portion of the appliance and is of a width enclosedby the thickness of the chamber element. The chamber element may beaffixed to the non-contacting portion of the tissue interfacing elementas an integral structure, unitary structure or discrete structures. An“integral structure” refers to a structure that is a complete pieceformed by joining two or more components which, once joined, become asingle piece that is not separable without destroying the device. A“unitary structure” refers to a structure that is a singular structureformed or molded as a single piece. Two elements are “discretestructures” if the two (or more) structures form a single workingstructure, but retain individual characteristics and can be separated inthe normal course of use of the single working structure and thenreassembled.

Surface variation of the therapy site, both permanent and occasional(i.e., the shape of the mandible, transition points from neck tomandible, tissue types, scars, facial hair and/or tissue blemishesdifferential forces applied to different portions of the seal caused bymovement of the wearer, etc.) can undesirably disrupt the seal betweenthe negative pressure therapy device and user. The present inventionprovides devices, systems and methods of use that can accommodatevarying facial contours/features and adapt to movement, resulting ingreater comfort, reduced vacuum leakage and improved therapeuticefficacy.

The flexible membrane element and the sealing element of the applianceincorporate cantilever-like structures, hoop load-like structures and ora combination of the two, adapted to have sectional properties thatallow for stiffness, flexibility and uniform regional compliance and/orforce load on the tissue surface of the individual. As used herein,“regional compliance” refers to a property of the device that permitsthe device to “mold” itself to a surface and or surface variation on thecontact surface with the wearer. As described hereinafter, uniformregional compliance is provided, in part, by the sectional properties orstructural features associated with a region on the chamber element,sealing element or both.

The sealing element may be in the form of a flange comprising aflexible, elastic material that can be uniform in thickness and widthbut also vary in thickness and width to achieve the structuralproperties desired at locations along the contact surface of the therapydevice. Further, the location of the chamber element at the rootlocation of the flange of the sealing element may be varied to adjustand equalize the contact pressure of the therapy device when atherapeutic level of negative pressure is applied. U.S. ProvisionalPatent Application No. 62/281,063 filed: Jan. 20, 2016, titled: “Deviceand Method for Opening an Airway,” and incorporated herein by reference,discusses variation of flange and chamber characteristics for thebalancing of contact pressure

In certain embodiments the sealing element may be a compliant tissueinterface element containing one or a series of layers, including afoamed silicone rubber layer to provide for a cushioning surface. Theinner surface of the flange being that which makes contact with theflexible membrane element and the outer surface of the compliant tissueinterface element being that which makes contact with the tissue of theuser. U.S. Provisional Patent Application No. 62/260,211 filed, Nov. 25,2015 titled: “Chamber Cushion, Seal and Use Thereof”, incorporatedherein by reference discusses such a cushioned sealing element.

The tissue interface portion of the appliance is adapted to havesectional properties that allow for flexibility and uniform regionalcompliance. As used herein, “uniform regional compliance” refers to aproperty of the compliant tissue interface element that permits thecompliant tissue interface element to “mold” itself to a surface and orsurface variation on the contact surface with the wearer. As describedhereinafter, this uniform regional compliance is provided, in part, bythe sectional properties or features associated with a region on thecompliant tissue interface element.

The compliant tissue interface element comprises a fluidly-sealed foamedsilicone rubber layer. The term “fluidly sealed” refers to a foamedsilicone rubber layer that precludes air from transmitting through thecompliant tissue interface element for a period of time required fornormal use of the chamber. By way of example, a latex balloon is“fluidly sealed” to helium if normal use of the balloon is for 6 hours,despite the fact that over time that helium may ultimately leak from theballoon, and despite the fact that the balloon may burst if put underabnormal conditions.

In certain embodiments, the sealing element of the invention provides acontact interface of a negative pressure therapy device configured toconform to a continuous contact area on the individual at the externalarea of the neck approximately corresponding to the anterior triangle ofthe neck. The term “approximately corresponding to” an anatomicallocation refers to contacting closely to the actual location, shape orsize but perhaps not necessarily completely, accurately or exactly.

Most preferably, the sealing element is configured to follow the contourof the therapy device which is designed to approximately conform to anindividual from approximately a first location corresponding to a firstgonion on one side of the individuals mandibular body to a secondlocation corresponding to the individuals mental protuberance to a thirdlocation corresponding to the second gonion on the opposite side of theindividual's mandibular body and a fourth location corresponding to theindividuals thyroid cartilage further configured to return toapproximately the first location corresponding to the first gonion.

The gonion, as used herein, describes the approximate location on eachside of the lower jaw on an individual at the mandibular angle. Themandibular protuberance, as used herein, describes the approximatelocation of the chin, the center of which may be depressed but raised oneither side forming the mental tubercles. The thyroid cartilage, as usedherein, describes the approximate location of the large cartilage of thelarynx in humans.

The sealing element and chamber element are designed to create uniformcontact pressure onto the tissue of the user when a therapeutic level ofpressure is applied. The sealing element is preferably a perpendicularwidth (wide and narrow) and thickness to achieve the desired contactpressure properties. The perpendicular width component is the totalwidth of the sealing, from the tip of the outside edge of the sealingelement through the root and to the tip of the inside edge of thesealing element. The width of sealing element may vary along theperipheral axis of the contact area of the sealing element toaccommodate for station load variations due to non-uniform shape of thetherapy device that contains a chamber that is oval in shape and furthercontains a central bend to accommodate the mating surface on the neck ofthe patient corresponding to approximately the upper airway and maintaina constant contact pressure of the negative pressure therapy device.

In various embodiments of the sealing element, locations on the flangeelement of the device may be substantially wider than other locations.In one aspect the total flange width may vary from approximately 28.0millimeters to approximately 17.0 millimeters. “Substantially wider” asused herein refers to an increase in width of at least about 10%, morepreferably at least about 20%, and still more preferably at least about30% or more from one location to another, for example in an embodimentof the invention the width of the flange element at the fourth locationcorresponding to approximately the middle of the neck of the user isapproximately 39% wider than the first and third locations thatcorresponding to the mandible and gonion regions of the user. Widersections may be found in regions where a larger load displacement isneeded for example at the second and fourth locations and narrowersections may be found in regions where smaller load displacement isneeded for example at the first and third locations on the user.

The thickness of the flange element may also vary along theperpendicular width along the circumference of contact surface of thetherapy device to accommodate for anatomical variation and varyingvacuum cross section. As used herein, thick or thin, describes thedistance between the surface of the flange contacting the individual andthe (distal) surface of the flange element contacting the chamberelement of the vacuum chamber of a negative pressure therapy device. Thethickness of the flange element at the root may vary from approximately4.5 millimeters to 1.0 millimeters at the inside of the root and 3.0millimeters to 1.2 millimeters at the outside of the root. For example,the thickness of the flange element at the junction at the first andthird locations on the user may be about 1.6 millimeters inside the rootand 2.10 millimeters outside the root.

In certain aspects, locations on the flange element of the device mayvary in thickness such that some portions are substantially thicker thanothers. For example, locations of the flange element may vary inthickness such that one location is substantially thicker than another.As used herein, “substantially thicker” refers to an increase inthickness of at least about 20%, more preferably at least about 30%, andstill more preferably at least about 50% or more. For example, in anembodiment of the invention the thickness at approximately the secondlocation is approximately 64% thicker that the first and third locationsand the first and third locations are approximately 30% thicker than thefourth location.

The thickness of the flange element may further taper outwardly from theroot location to a final flange thickness of approximately 0.7millimeters to approximately 0.1 millimeters. The taper may begin at theroot continuing to the inside or outside edge of the flange or the tapermay also begin at points about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%,50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% away from the tip ofthe flange element and continue to the inside or outside edge of theflange element to a desired final thickness of approximately 0.7-0.1millimeters. The taper of the flange at its inner and outer edgesassisting in the elimination of edge effects, allowing for minimizedtissue irritation and damage. As used herein, “edge effects” refer tothe irritation, (redness, swelling) of tissue caused by prolongedcontact pressure of a sharp edge on the tissue. The tapering of edgesprovides for a more flexible and softer edge of the flange

The chamber element is stiff along its length and the flange will notappreciably deflect longitudinally. Therefore in addressing the dynamicshape of the target therapy area, regions of the therapy device containaccommodating design features, for example, the variations in the widthand thickness of the flange element, and or the addition of thecompliant conforming interface that are designed to minimize highpressure points and eliminate contact pressure variations of the therapydevice along its contact surface when placed on the user and atherapeutic level of negative pressure is applied.

In regions where the flange contacts a substantially flat surface of theuser, the chamber element and flange element can act as an “I-beam”where the force exhibited by the flange on the user is a more lineardownward force and cantilever-like. The flange element inside andoutside the root point of the chamber element flex according to thethickness of material with the tapered ends of the flange elementflexing the most creating a soft transition on the tissue of the usereliminating edge effects as above. As used herein cantilever-like forcesare a measurement of the downward force of the chamber divided by thearea of the flange at a given point. By way of example, in regions wherethe flange element lays flat across the tissue, cantilever forces can bebalanced by altering the width and thickness of the flange, for examplewhere there is a high vacuum cross section and where larger loaddistribution is desired (i.e. lower contact pressure), a flange with alarger perpendicular width may be utilized and similarly in regionswhere a smaller load distribution is desired (i.e. higher contactpressure) a flange with a smaller perpendicular width may be utilized

The thickness dimensions of the flange element can give the flangeelement properties such that in portions of the device, if the flangeelement is too thin, though it may be very flexible it will have littleto no load distributing properties, can bottom out creating point(s) ofhigh contact pressure from the root of the chamber element resulting inleaks and/or discomfort. If the flange element is too thick it willaffect its ability to change direction for example be unable to conformto the acute change from the surface of the neck over the mandibletoward the ear for example and further allow for an undesirable level ofsheer or lateral movement. In a similar fashion, if the width of theflange element is too small it can create a point(s) of high pressureand too wide it may create unnecessary bulk affecting fit and effectivetherapy area. Transition in widths taper gradually and the aspect ratiominimizes positional instability and optimizes flexibility.

In regions where the flange contacts a curved surface of the user, forexample around the chin and over the mandible, the forces observedcontain an additional hoop-like force component as the flange bendsaround those features. “Hoop-like forces” as used herein describe thedistribution of force exerted circumferentially, for example, as theflange element travels around location four of the user, the curvatureadds additional stiffness to the flange inside and outside the root ofthe chamber element. In these regions where the added force component ofhoop loads exists, the thickness of the flange element may be decreasedand the perpendicular width of the flange element may be increased toeffectively distribute the load of the chamber and minimize contactpressure variation from station to station when a therapeutic level ofnegative pressure is applied.

The term “contact pressure” as used herein refers to a pressure impartedon the surface of the tissue by the contact surface of the device. Itsvalue can depend on the vacuum present as well as the structuralcharacteristics of the flange such as the perpendicular width andsurface area of the contact surface, and can vary at different locationson the flange.

A larger “perpendicular width” of a contact surface (meaning thedirection that is perpendicular to the longest axis of the contactsurface, which longest axis may be curved) will have a lower overallcontact pressure under the same vacuum pressure as a contact surfacewith a smaller perpendicular width due to the increased surface area atthat particular station of the contact surface. Therefore, in regionswhere the dome station pressure load is low, the contact surface of theflange can be designed to be of a smaller perpendicular width toeffectively increase and “balance” the contact pressure and in regionswhere the dome station pressure is high, the contact surface of theflange can be designed to be of a larger perpendicular width toeffectively decrease and balance the contact pressure where the domestation load is high.

In certain embodiments the location of the chamber element on the flangeelement (the root location) may vary from the mid-point, inward oroutward to further aid in equalizing the contact pressure of the therapydevice on the user when a therapeutic level of negative pressure isapplied creating and maintaining the balance point of the flange elementon the user. For example, movement of the root of the edge of chamberelement on the flange element outward from the mid-point of the flangeelement effectively increases the vacuum cross section and thereforeeffective contact pressure of the therapy device at that point when atherapeutic level of negative pressure is applied. Movement of the edgeof the chamber inward has an opposing effect, providing a larger portionof the flange exposed outside the root location and therapy areadecreasing the vacuum cross section. In regions where higher contactpressure is needed, for example where the device approaches the ear ofthe user, the chamber location can be biased on the flange toward theouter edge increasing the vacuum cross section and effective contactpressure at that point.

The chamber is operably connected to an air pump to produce thetherapeutic level of negative pressure within the chamber element. Theair pump can be of any type suitable to produce the therapeutic level ofnegative pressure, for example positive displacement pumps, impulsepumps, velocity pumps, etc which can include manual squeeze bulbs,rotary pumps, lobe pumps, oscillatory pumps etc. In certain embodimentsthe air pump comprises a piezoelectric material configured to provide anoscillatory pumping action wherein the oscillatory pumping motionoperates at a frequency greater that 500 Hz.

The air pump may be a separate component connected to the chamber via ahose or tube or may be configured integrally to the chamber. The airpump can be connected to the chamber element in any suitable fashion,for example an air pump may be externally located outside of the chamberelement and connected via a hose or tube, e.g. a stationary bed-sidepump, or the pump may be integral to chamber, be battery powered, andwearable by the patient. In certain wearable aspects, the air pump isconfigured to be integral to the chamber. For example, the air pump maybe configured to insert into a sealable aperture on the chamber, the airpump tightly fitting through the aperture creating a seal. As usedherein a sealable aperture is an opening through an element of theapparatus that can be closed or sealed from one side or the other withanother element of the apparatus creating an air-tight or water tightseal.

In certain embodiments, together or with one or more of the foregoing, amaterial, which will act as an adhesive layer between the flange elementof the therapy device and the user, is applied to the outer contactsurface of the flange element. The purpose of the adhesive layer is toprovide a sealing, cushioning and/or sheer absorbing (i.e. abrasionresistant) element to the flange element. As used herein sheer refers tosheer strain which is a deformation of a material in which parallelsurfaces can slide past one another, for example the contact surface ofthe flange element and the tissue of the user.

The adhesive layer further must preferentially adhere to the outercontact surface of the negative pressure therapy device and provide asufficient level of “tack” such that a releasable mechanical anchoringof the therapy device to the tissue of the user is achieved. Tack, asused herein, refers to a material property at the interface createdbetween the adhesive layer and the device, and the tissue of the user atthe other interface created between the user and the device.

The adhesive layer may be applied to the contact surface area of thenegative pressure therapy device in any suitable method including butnot limited to spraying, painting, placing, etc., in single or multiplelayers to achieve the desired cushioning and sealing propertiesincluding but not limited to thickness, hardness and tack for example.In additional embodiments the adhesive layer may be single layer of auniform thickness or a single layer of a non-uniform thickness coveringthe contact surface of the negative pressure therapy device. In furtherembodiments the adhesive layer may contain a series of parallel adhesivebeads spanning the circumference of the contact surface of the negativepressure therapy device wherein the beads can be of a uniform ornon-uniform thickness and of a like or varying adhesive and or gel-likematerial to achieve the desired cushioning and sealing properties.

In certain embodiments an adhesive layer is present on the contactsurface of the negative pressure therapy device at a thickness fallingwithin a range of approximately 0.005-0.060 inches. In certainembodiments the adhesive layer is present on the contact surface of thenegative pressure therapy device at a thickness falling within a rangeof approximately 0.010-0.050 inches. In further embodiments the adhesivelayer is present on the contact surface of the negative pressure therapydevice at a thickness falling within a range of approximately0.020-0.040 inches.

The adhesive layer may be achieved by using various materials, such as,but not limited to gel, elastomer, viscous solutions, foams andmaterials of the like. These materials can be of any chemicalcomposition which provides the necessary end use properties (i.e. tack,firmness, medical clearance, etc.). These materials include, but are notlimited to polyurethanes, silicones, acroylnitrile butadiene styrene(ABS), hydrogels, and the like. In preferred embodiments, the adhesivelayer should have a hardness as measured by ASTM-D2240-00 (AmericanSociety for Testing Materials) of between 0 and 50, more preferablebetween 5 and 30 most preferable between 5 and 15. In certainembodiments the adhesive layer is made of a silicone gel material. Thesilicone can be any organosilicone which yields the desired propertiesalthough polydimethylsiloxane (PDMS) is often chosen.

The adhesive layer may be applied directly to the outer contact surfaceof the flange element to a desired thickness or in combination with oneor more primer layer and or one or more primer layers in combinationwith one or more adhesion or binding promotor layers to create alamination stack of materials to a desired thickness. As used herein a“primer” is a substance used as a preparatory coating, acting as ajoining surface between the contact surface of the negative pressuretherapy device and adhesive layer or an adhesion promoting layer and theadhesive layer. Further, an adhesion promoting layer is a substance usedas a coating to preferentially adhere the adhesive layer to the contactsurface of the negative pressure therapy device and or the primer layerthat is applied to the outer surface of the negative pressure therapydevice.

By way of example, a primer layer may be applied to the contact surfaceof the negative pressure therapy device to a thickness of about 0.005inches, followed by an adhesive promoting layer to a thickness ofapproximately 0.005 inches, followed by the application of an adhesivelayer to a thickness of approximately 0.040 inches achieving a finalthickness of approximately 0.050 inches. A primer layer may be applieddirectly to the outer contact surface of the negative pressure therapydevice followed by the application of the adhesive layer directly to theprimer to a desired thickness of approximately 0.050 inches. Inadditional embodiments, an adhesive promoter may be applied to thecontact surface of the negative pressure therapy device followed by theapplication of the adhesive layer to a desired thickness ofapproximately 0.050 inches.

In certain embodiments the adhesive layer is a gel layer. As used hereina gel layer is a layer of material that can have properties that aremostly liquid however behave like solids due to the cross-linked natureof its structure. The material chosen for the gel layer may be of acertain cohesive pliable consistency so as to mold to and conform tocomplex shapes for example imperfections in the tissue. As used hereincohesive pliable consistency, elasticity or firmness of the gel layer isdefined as the gel layer's ability to flow, mold and stretch andsubstantially return its original shape when not applied to a surface.The material chosen for the gel layer may also be of a certain tack soas to mechanically secure to the contact area. As used herein tack isdefined as the gel's “stickiness” and is the property that allows theimmediate formation of a bond on contact with another surface

The adhesive layer material must adhere sufficiently to the therapeuticdevice such that it stays adhered to the device when the device isremoved from the user's tissue. Additionally, must have a tack levelthat is chosen for appropriate performance at the user's tissueinterface. That is, at too great a level of tack removal of the devicefrom the tissue can be difficult, painful or injurious. Whileinsufficient tack can allow the device to move during use or allow theseal to the tissue to open thereby losing the vacuum. The level of tackcan be measured by a texture analyzer. For example, using a TA.XT pluswith a 7 mm radius and 1 inch diameter spherical head the peak adhesionvalues should be in a range of 200 to 400 grams peak force morepreferably 250 to 350 grams peak force and most preferably 275-325 gramspeak force.

As discussed above the tack of the adhesive layer is optimized toachieve a releasable but mechanical anchor of the therapy device to thepatient. In certain embodiments the contact surface of the flangeelement is coated with a primer to preferentially anchor the adhesivelayer to the negative pressure therapy device over the contact region ofthe user.

In certain embodiments the adhesive layer is formed from a washablesilicone gel such that when washed and allowed to dry, the adhesivelayer returns towards an initial tack. In certain embodiments thesilicone gel is chosen from a group with properties that can becontrolled including, but not limited to: cross sectional thickness,degree of crosslinking (and thereby firmness and tack) and viscosity (soas to be processable under desired conditions. As used herein viscosityis measured in cps referring to centipoise (cps) were 1 cps=0.01 g/cm/s.

In an embodiment of the invention the gel layer is prepared from atwo-part platinum cured organosilicone mixture with propertiesequivalent to a silicone gel base having an uncatalyzed viscosity ofabout 31,000 cps and a crosslinker having an uncatalyzed viscosity ofabout 30,500 cps. The final firmness (cps) of the cured gel may beincreased by increasing the proportion of the crosslinker in the mixtureor decreased by lowering the proportion of the crosslinker in the mix.The tack of the material can be increased by decreasing the proportionof crosslinker in the mixture or decreased by increasing the proportionof crosslinker in the mix. In order to achieve the desired propertiesusing a silicone gel base of 31,000 cps and a crosslinker of 0,500 cps,the ratio of silicone gel base to crosslinker may range (in parts byweight) from about 0.8:1 to about 1:0.8.

In embodiments of the invention the ratio of 31,000 cps silicone gelbase to 30,500 cps cross linker may further range from about 1:0.8 toabout 1:1. In other embodiments of the invention the ratio of 31,000 cpssilicone gel base to 30,500 cps crosslinker may range from about 0.8:1to about 1:1. And in further embodiments of the invention the ratio of31,000 cps silicone gel base to 30,500 cps crosslinker may range fromabout 0.88:1 to about 1:0.88.

By example of the invention the silicone gel base and the crosslinkerare mixed in desired ratios and placed under vacuum in order to removeany bubbles in the mixed solution (de-gassing). Following de-gassing,the silicone gel solution is applied to the contact surface of theflange element and allowed to cure. The mixture can achieve full cure inapproximately 24 hours at room temperature however in some embodiments afull cure ^(of) the silicone gel may be achieved in about 5 minutes byplacing the therapy device containing the silicone gel layer at about150° C. The cure temperature may be adjusted to suit limiting elementsof the therapy device, for example lower melting points of other therapydevice elements.

In certain embodiments the adhesive layer is made of a hydrogel.Hydrogels are a three-dimensional network of crosslinked hydrophilicpolymer chains that can be crosslinked either physically or chemically.In further embodiments the hydrogel layer may be found as a hydrocolloidwherein the colloid particles are hydrophilic polymers dispersed inwater.

In certain embodiments the adhesive layer is made of a combination ofmaterials or similar materials with differing mechanical properties forexample differing durometers applied side-by side on the outer contactsurface of the fluidly sealed chamber. By way of example, a hydrogelmaterial may be applied to the circumference of the center portion ofthe outer contact surface of the fluidly sealed chamber and a siliconegel material may be applied on either side peripheral to the hydrogelmaterial. In further embodiments where a combination of materials areapplied side-by-side on the outer contact surface of the flange element,a silicone gel layer may be applied to the circumference of the centerportion of the out contact surface of the fluidly sealed chamber and ahydrogel material may be applied to either side peripheral to thesilicone gel material followed by a final application of a silicone gelmaterial peripheral to the hydrogel material.

In certain embodiments, the compliant contact layer is made of acombination of materials applied side-by side on the outer contactsurface of the fluidly sealed chamber. By way of example, a hydrogelmaterial may be applied to the circumference of the center portion ofthe outer contact surface of the fluidly sealed chamber and a siliconegel material may be applied on either side peripheral to the hydrogelmaterial. In further embodiments where a combination of materials areapplied side-by-side on the outer contact surface of the flange element,a silicone gel layer may be applied to the circumference of the centerportion of the outer contact surface of the fluidly sealed chamber and ahydrogel material may be applied to either side peripheral to thesilicone gel material followed by a final application of a silicone gelmaterial peripheral to the hydrogel material.

As used herein, “user compliance” refers to the patient's adherence tothe prescribed usage of a therapy device for example the usage of adevice throughout a sleep cycle.

As used herein, “device compliance” refers to the ability of the deviceor elements of the device to accommodate variation, for example,bending, twisting, compressing and or expanding of the device inresponse to device application and usage including anatomical variationsand or movement of the patient.

Aspects of the device may be made of a generally rigid material. Theterm “generally rigid” as used herein refers to a material which issufficiently rigid to maintain the integrity of the particular elementin question. The skilled artisan will understand that a number ofpolymers may be used including thermoplastics, some thermosets, andelastomers. Thermoplastic materials become flowing liquids when heatedand solids when cooled, they are often capable of undergoing multipleheating/cooling cycles without losing mechanical properties. Thermosetmaterials are made of prepolymers which upon reaction cure irreversiblyinto a solid polymer network. Elastomers are viscoelastic materialswhich exhibit both elastic and viscous properties and can be either athermoplastic or thermoset. Common thermoplastics include PMMA, cyclicolefin copolymer, ethylene vinyl acetate, polyacrylate,polyaryletherketone, polybutadiene, polycarbonate, polyester,polyetherimide, polysulfone, nylon, polyethylene, and polystyrene.Common thermosets include polyesters, polyurethanes, duroplast, epoxyresins, and polyimides. This list is not meant to be limiting.Functional filler materials such as talc and carbon fibers can beincluded for purposes of improving stiffness, working temperatures, andpart shrinkage.

Aspects of the device may be formed using a number of methods known tothose of skill in the art, including but not limited to casting,injection, transfer, and compression molding, coating, machining,etching, 3D printing, etc. In preferred embodiments, the test devicebase is injection molded, a process for forming thermoplastic andthermoset materials into molded products of intricate shapes, at highproduction rates and with good dimensional accuracy. The processtypically involves the injection, under high pressure, of a meteredquantity of heated and plasticized material into a relatively coolmold-in which the plastic material solidifies. Resin pellets are fedthrough a heated screw and barrel under high pressure. The liquefiedmaterial moves through a runner system and into the mold. The cavity ofthe mold determines the external shape of the product while the coreshapes the interior. When the material enters the chilled cavities, itstarts to re-plasticize and return to a solid state and theconfiguration of the finished part. The machine then ejects the finishedparts or products.

The following represent preferred embodiments of the invention:

1. An appliance configured to contact tissue, comprising:

(a) a tissue interface portion comprising a viscoelastic foam configuredto provide a tissue contact surface of the appliance, wherein theviscoelastic foam comprises one or more of the following properties:a Shore A of about 10 or less and preferably a Shore 00 durometer ofabout 30 or less, more preferably of about 20 or less, and still morepreferably of about 10 or less, as measured using the Standard TestMethod for Rubber Property—Durometer Hardness ASTM D2240-15;a density (specific gravity) of about 0.9 g/cm³ or less; and/ora level of tack measured using the Standard Test Method forPressure-Sensitive Tack of Adhesives ASTM D2979-16 of about 9 mJ/cm² orless, preferably about 7 mJ/cm² or less, most preferably about 5 mJ/cm²or less;an elastic (storage) modulus of between about 0.3 kPa to about 30 kPa,and preferably between about 1 kPa and about 15 kPa;a viscous (loss) modulus of between about 0.4 kPa to about 7 kPa, andpreferably between about 0.8 kPa and about 7 kPa; and(b) a non-contacting portion configured to support the tissue interfaceportion and to be separated from the tissue by the tissue interfaceportion, wherein one or more of (i), (ii), (iii), and (iv) is true:

-   -   (i) the tissue interface portion comprises a siloxane        antimicrobial material coated onto or molded into the        viscoelastic foam;    -   (ii) the tissue interface portion is overmolded on the        noncontacting portion;    -   (iii) the tissue interface portion is attached to the        noncontacting portion using a silicone pressure-sensitive        adhesive; and    -   (iv) tissue interface portion comprises one of more filler        materials having a higher thermal conductivity than the        viscoelastic foam material.

2. An appliance according to embodiment 1, wherein the viscoelastic foamcomprises one or both of an elastic (storage) modulus of between about10 kPa and about 15 kPa and a viscous (loss) modulus of between about 2kPa and about 7 kPa.

3. An appliance according to embodiment 1 or 2, wherein the appliancefurther comprises a second tissue contact surface that is not aviscoelastic foam.

4. An appliance according to one of embodiments 1-3, wherein theviscoelastic foam comprises a Shore A of about 10 or less, a density(specific gravity) of about 0.9 g/cm³ or less, and a level of tack ofabout 9 mJ/cm² or less.

5. An appliance according to one of embodiments 1-4, wherein the foamcomprises a Shore A of about 5 or less.

6. An appliance according to one of embodiments 1-4, wherein the foamcomprises a Shore A of about 1 or less.

7. An appliance according to one of embodiments 1-6, wherein theviscoelastic foam does not include a tackifier or an adhesive andwherein the tack is an inherent property of the viscoelastic foam.

8. An appliance according to one of embodiments 1-7, wherein theviscoelastic foam exhibits a tack of at least about 0.1 mJ/cm², at leastabout 0.3 mJ/cm², or at least about 0.5 mJ/cm².

9. An appliance according to one of embodiments 1-8, wherein theviscoelastic foam provides an air leakage past the sealed surface of nomore than about 8 mL/min at atmospheric pressure.

10. An appliance according to one of embodiments 1-8, wherein theviscoelastic foam provides an air leakage past the sealed surface of nomore than about 0.8 mL/min at atmospheric pressure.

11. An appliance according to one of embodiments 1-8, wherein theviscoelastic foam provides a seal to the tissue, and an air leakage pastthe seal of no more than about 0.008 mL/min at atmospheric pressure.

12. An appliance according to one of embodiments 1-11, wherein theviscoelastic foam has a density of about 0.5 g/cm³ or less.

13. An appliance according to one of embodiments 1-12, wherein theviscoelastic foam is a foamed silicone rubber, optionally wherein thesilicone rubber component of the viscoelastic foam is a medical-gradesoft skin adhesive (SSA) silicone.

14. An appliance according to one of embodiments 1-13, wherein theviscoelastic foam comprises a reinforcing filler.

15. An appliance according to embodiment 14, wherein the reinforcingfiller is selected from the group consisting of silica, silica aerogel,silica xerogel, titanium dioxide, diatomaceous earth, iron oxide,aluminum oxide, zinc oxide, quartz, calcium, carbonate, magnesium oxide,carbon black, graphite, glass fibers, glass micro spheres, glass microballoons, glass beads, carbon fibers, silicon carbide, polystyrenebeads, microcrystalline cellulose, nanoparticles and metal fibers.

16. An appliance according to one of embodiments 1-15, wherein theviscoelastic foam comprises an antimicrobial agent.

17. An appliance according to embodiment 16, wherein the antimicrobialagent comprises one or more agents selected from the group consisting ofsilver salts, silver ions, silver ions encapsulated in a glass particle,silver sodium zirconium hydrogenphosphate, 3-(Trimethoxysilyl)propyldimethyl octadecyl ammonium chloride, benzalkonium chloride,benzethonium chloride, and chloroxylenol, polyhexamethylenebiguanide(PHMB) and chlorhexidine.

18. An appliance according to one of embodiments 1-17, wherein (i) istrue.

19. An appliance according to one of embodiments 1-18, wherein (ii) istrue.

20. An appliance according to one of embodiments 1-19, wherein (iii) istrue.

21. An appliance according to one of embodiments 1-20, wherein (iv) istrue.

22. An appliance according to one of embodiments 1-21, wherein theappliance is an eye protection mask.

23. An appliance according to one of embodiments 1-21, wherein theappliance is a SCUBA mask

24. An appliance according to one of embodiments 1-21, wherein theappliance is a swim goggle.

25. An appliance according to embodiment 23 or 24, wherein theviscoelastic foam provides a seal to the tissue, and a water leakagepast the seal such that at a pressure of 1 atm, the appliance leaks nomore than 10% of the internal volume of the appliance in 10 minutes.

26. An appliance according to one of embodiments 1-21, wherein theappliance is a medical appliance.

27. An appliance according to one of embodiments 1-21, wherein theappliance is a breathing mask.

28. An appliance according to one of embodiments 1-21, wherein themedical appliance is a negative pressure chamber configured to covertissue of a human or animal body.

29. An appliance according to embodiment 28, wherein the medicalappliance is a negative-pressure wound therapy device.

30. An appliance according to embodiment 28, wherein the negativepressure chamber is a continuous negative external pressure (cNEP)therapy device for maintenance of airway patency by the application ofan external negative pressure to tissue overlying a portion of a humanairway.

31. An appliance according to one of embodiments 1-21, wherein theappliance is a set of headphones, ear plugs, ear buds, or earphones.

32. An appliance according to one of embodiments 1-21, wherein theappliance is a catheter, a vascular stent, a vascular graft, a vascularstent-graft, or components thereof.

33. A method of forming a viscoelastic foam providing a tissue contactsurface of an appliance according to one of embodiments 1-32,comprising:

combining a silicone base, a foaming agent, and a catalyst to provide aformulation;curing the formulation under conditions selected to provide theviscoelastic foam, wherein the viscoelastic foam has one or more of thefollowing properties:a Shore A of about 10 or less, and preferably a Shore 00 durometer ofabout 30 or less, more preferably of about 20 or less, and still morepreferably of about 10 or less, in each case as measured using theStandard Test Method for Rubber Property—Durometer Hardness ASTMD2240-15;a density (specific gravity) of about 0.9 g/cm³ or less; and/ora level of tack measured using the Standard Test Method forPressure-Sensitive Tack of Adhesives ASTM D2979-16 of about 9 mJ/cm² orless, preferably about 7 mJ/cm² or less, most preferably about 5 mJ/cm²or less;an elastic (storage) modulus of between about 0.3 kPa to about 30 kPa,and preferably between about 1 kPa and about 15 kPa;a viscous (loss) modulus of between about 0.4 kPa to about 7 kPa, andpreferably between about 0.8 kPa and about 7 kPa.

34. A method according to embodiment 33, wherein the curing stepcomprises curing at a temperature between about 100° C. and about 250°C.

35. A method according to embodiment 34, wherein the curing stepcomprises curing at a temperature of at least about 120° C.

36. A method according to embodiment 34, wherein the curing stepcomprises curing at a temperature of at least about 150° C.

37. A method according to embodiment 34, wherein the curing stepcomprises curing at a temperature of at least about 170° C.

38. A method according to one of embodiments 33-37, wherein the foamingagent comprises an ammonium salt, a sodium salt, or a potassium salt.

39. A method according to one of embodiments 33-38, wherein the catalystis selected from the group consisting of an iron catalyst, a cobaltcatalyst, a zinc catalyst, a titanate catalyst, a tin catalyst, aplatinum catalyst, or an acid catalyst.

40. A method according to one of embodiments 33-39, wherein theviscoelastic foam comprises one or both of an elastic (storage) modulusof between about 10 kPa and about 15 kPa and a viscous (loss) modulus ofbetween about 2 kPa and about 7 kPa.

41. A method according to embodiment 40, wherein the viscoelastic foamcomprises a Shore A of about 10 or less, a density (specific gravity) ofabout 0.9 g/cm³ or less, and a level of tack of about 9 mJ/cm² or less.

42. A method according to embodiment 41, wherein the foam comprises aShore A of about 5 or less.

43. A method according to embodiment 41, wherein the foam comprises aShore A of about 1 or less.

44. A method according to one of embodiments 33-43, wherein theviscoelastic foam does not include a tackifier or an adhesive.

45. A method according to one of embodiments 33-44, wherein theviscoelastic foam exhibits a tack of at least about 0.1 mJ/cm², at leastabout 0.3 mJ/cm², or at least about 0.5 mJ/cm².

46. A method according to one of embodiments 33-45, wherein an outersurface of the viscoelastic foam is skinned-over to form a closed cellregion of the viscoelastic foam.

47. An appliance according to embodiment 46, wherein the viscoelasticfoam is coated with a thin elastomer of less than 40 durometer and inratios less than 1:10 to produce a dual durometer structure.

48. An appliance according to embodiments 46, wherein the viscoelasticfoam is coated with a medical-grade SSA silicone of less than 40durometer and in ratios less than 1:10 to produce a dual durometerstructure.

49. A method according to one of embodiments 33-48, wherein the siliconebase is an LSR.

50. A method according to one of embodiments 33-48, wherein the siliconebase is an HCR.

51. A method according to one of embodiments 33-50 wherein one or moreof (i), (ii), (iii), and (iv) is true:

-   -   (i) the tissue interface portion comprises a siloxane        antimicrobial material coated onto or molded into the        viscoelastic foam;    -   (ii) the tissue interface portion is overmolded on the        noncontacting portion;    -   (iii) the tissue interface portion is attached to the        noncontacting portion using a silicone pressure-sensitive        adhesive; and    -   (iv) tissue interface portion comprises one of more filler        materials having a higher thermal conductivity than the        viscoelastic foam material.

52. An appliance according to embodiment 51, wherein (i) is true.

53. An appliance according to one of embodiments 51 or 52, wherein (ii)is true.

54. An appliance according to one of embodiments 51-53, wherein (iii) istrue.

55. An appliance according to one of embodiments 51-54, wherein (iv) istrue.

Example 1—Liquid Silicone Rubber and Foaming Agent

Material preparation was done using a 10 Shore A durometer liquidsilicone rubber (Silbione® LSR 4310, Elkem Silicones USA) and anammonium bicarbonate foaming agent (Med4-4900, Nusil Technology LLC).The liquid silicone rubber used is a two component platinum-catalyzedsilicone elastomer that was manually mixed in a 1:1 ratio. The ammoniumbicarbonate was measured out at 1.5% by weight of the liquid siliconerubber mixture, then combined and manually blended together with it.

Example 2—Liquid Silicone Rubber and Foaming Agent with AntimicrobialAdditive

Material preparation was done using a 5 Shore A durometer liquidsilicone rubber (Silbione® LSR 4305, Elkem Silicones USA), an ammoniumbicarbonate foaming agent (Med4-4900, Nusil Technology LLC), and asilicone-based antimicrobial additive (BIOSAFE® HM 4001, Gelest, Inc.).The liquid silicone rubber used is a two component platinum-catalyzedsilicone elastomer that was manually mixed in a 1:1 ratio. The ammoniumbicarbonate was measured out at 1.5%, and the organosilane antimicrobialwas measured out at 0.5%, each by weight of the liquid silicone rubbermixture. These were combined and manually blended together with theliquid silicone rubber mixture.

Whether the material was compounded as noted in Example 1 withoutantimicrobial additive, or as in Example 2 with antimicrobial additive,material forming was done using a knife coating machine. Knife coatingis a process by which a thin liquid coating is formed on a continuouspolymer web substrate by the application of an excess of coating liquidthat is subsequently metered by a rigid knife held in close proximity tothe rigidly supported web as the web advances. The thickness of thecoating depends primarily on the clearance or gap between the knife andthe web, and upon the geometry of the gap (bevel angle, length, etc.).In this embodiment, an excess of the liquid silicone rubber and ammoniumbicarbonate mixture described above was applied to the advancing web,upstream of a knife that was set to a gap of 2.16 mm clearance. As theweb advanced, the metered 2.16 mm thickness portion of the web wasexposed to 150° C. heat intended to simultaneously activate the foamingand cure the liquid silicone rubber. Heating was maintained for aminimum period of 5 minutes, during which time the ammonium bicarbonatefoaming caused the material to swell in thickness. After the 5 minuteheating period, the cured elastomeric foam was allowed to return to roomtemperature where the resultant foam thickness settled to a nominal 3.05mm.

Material application was accomplished by die cutting the elastomericfoam sheet into an appropriate 2-dimensional shape (i.e. roughly a 114mm×190 mm oval donut having a 25 mm wide annulus) that corresponded withthe 3-dimensional shape of the tissue contacting flange of a negativepressure appliance. Once die cut into shape, the polymer web backing wasremoved from the backside of the elastomeric foam donut and a uniformthin coating of silicone rubber adhesive (Sil-Poxy®, Smooth-On, Inc.)was manually applied in its place along its entire annulus. A uniformthin coating of silicone rubber adhesive was manually applied on theflange of the negative pressure appliance as well. The coatedelastomeric foam donut was subsequently manually manipulated to alignand press it into place on the flange of the negative pressureappliance. The silicone rubber adhesive was allowed to cure at roomtemperature for a minimum of 12 minutes.

The end result was a negative pressure appliance with an elastomericfoam that continuously conformed with its tissue contacting flange.

Those skilled in the art will appreciate that the conception upon whichthis disclosure is based may readily be utilized as a basis for thedesigning of other structures, methods and systems for carrying out theseveral purposes of the present invention. It is important, therefore,that the claims be regarded as including such equivalent constructionsinsofar as they do not depart from the spirit and scope of the presentinvention.

One skilled in the art readily appreciates that the present invention iswell adapted to carry out the objects and obtain the ends and advantagesmentioned, as well as those inherent therein. The examples providedherein are representative of preferred embodiments, are exemplary, andare not intended as limitations on the scope of the invention.

It will be readily apparent to a person skilled in the art that varyingsubstitutions and modifications may be made to the invention disclosedherein without departing from the scope and spirit of the invention.

All patents and publications mentioned in the specification areindicative of the levels of those of ordinary skill in the art to whichthe invention pertains. All patents and publications are hereinincorporated by reference to the same extent as if each individualpublication was specifically and individually indicated to beincorporated by reference.

The invention illustratively described herein suitably may be practicedin the absence of any element or elements, limitation or limitationswhich is not specifically disclosed herein. Thus, for example, in eachinstance herein any of the terms “comprising”, “consisting essentiallyof” and “consisting of” may be replaced with either of the other twoterms. The terms and expressions which have been employed are used asterms of description and not of limitation, and there is no intentionthat in the use of such terms and expressions of excluding anyequivalents of the features shown and described or portions thereof, butit is recognized that various modifications are possible within thescope of the invention claimed. Thus, it should be understood thatalthough the present invention has been specifically disclosed bypreferred embodiments and optional features, modification and variationof the concepts herein disclosed may be resorted to by those skilled inthe art, and that such modifications and variations are considered to bewithin the scope of this invention as defined by the appended claims.

Other embodiments are set forth within the following claims:

What is claimed is:
 1. An appliance configured to contact tissue,comprising: (a) a tissue interface portion comprising a viscoelasticfoam configured to provide a tissue contact surface of the appliance,wherein the viscoelastic foam comprises one or more of the followingproperties: a Shore A of about 10 or less and preferably a Shore 00durometer of about 30 or less, more preferably of about 20 or less, andstill more preferably of about 10 or less, as measured using theStandard Test Method for Rubber Property—Durometer Hardness ASTMD2240-15; a density (specific gravity) of about 0.9 g/cm³ or less;and/or a level of tack measured using the Standard Test Method forPressure-Sensitive Tack of Adhesives ASTM D2979-16 of about 9 mJ/cm² orless, preferably about 7 mJ/cm² or less, most preferably about 5 mJ/cm²or less; an elastic (storage) modulus of between about 0.3 kPa to about30 kPa, and preferably between about 1 kPa and about 15 kPa; a viscous(loss) modulus of between about 0.4 kPa to about 7 kPa, and preferablybetween about 0.8 kPa and about 7 kPa; and (b) a non-contacting portionconfigured to support the tissue interface portion and to be separatedfrom the tissue by the tissue interface portion, wherein one or more of(i), (ii), (iii), and (iv) is true: (i) the tissue interface portioncomprises a siloxane antimicrobial material coated onto or molded intothe viscoelastic foam; (ii) the tissue interface portion is overmoldedon the non-contacting portion; (iii) the tissue interface portion isattached to the non-contacting portion using a siliconepressure-sensitive adhesive; and (iv) tissue interface portion comprisesone of more filler materials having a higher thermal conductivity thanthe viscoelastic foam material in the absence of the filler materials.2. An appliance according to claim 1, wherein the viscoelastic foamcomprises one or both of an elastic (storage) modulus of between about10 kPa and about 15 kPa and a viscous (loss) modulus of between about 2kPa and about 7 kPa.
 3. An appliance according to claim 1 or 2, whereinthe appliance further comprises a second tissue contact surface that isnot a viscoelastic foam.
 4. An appliance according to one of claims 1-3,wherein the viscoelastic foam comprises a Shore A of about 10 or less, adensity (specific gravity) of about 0.9 g/cm³ or less, and a level oftack of about 9 mJ/cm² or less.
 5. An appliance according to one ofclaims 1-4, wherein the foam comprises a Shore A of about 5 or less. 6.An appliance according to one of claims 1-4, wherein the foam comprisesa Shore A of about 1 or less.
 7. An appliance according to one of claims1-6, wherein the viscoelastic foam does not include a tackifier or anadhesive and wherein the tack is an inherent property of theviscoelastic foam.
 8. An appliance according to one of claims 1-7,wherein the viscoelastic foam exhibits a tack of at least about 0.1mJ/cm², at least about 0.3 mJ/cm², or at least about 0.5 mJ/cm².
 9. Anappliance according to one of claims 1-8, wherein the viscoelastic foamprovides an air leakage past the sealed surface of no more than about 8mL/min at atmospheric pressure.
 10. An appliance according to one ofclaims 1-8, wherein the viscoelastic foam provides an air leakage pastthe sealed surface of no more than about 0.8 mL/min at atmosphericpressure.
 11. An appliance according to one of claims 1-8, wherein theviscoelastic foam provides a seal to the tissue, and an air leakage pastthe seal of no more than about 0.008 mL/min at atmospheric pressure. 12.An appliance according to one of claims 1-11, wherein the viscoelasticfoam has a density of about 0.5 g/cm³ or less.
 13. An applianceaccording to one of claims 1-12, wherein the viscoelastic foam is afoamed silicone rubber, optionally wherein the silicone rubber componentof the viscoelastic foam is a medical-grade soft skin adhesive (SSA)silicone.
 14. An appliance according to one of claims 1-13, wherein theviscoelastic foam comprises a reinforcing filler.
 15. An applianceaccording to claim 14, wherein the reinforcing filler is selected fromthe group consisting of silica, silica aerogel, silica xerogel, titaniumdioxide, diatomaceous earth, iron oxide, aluminum oxide, zinc oxide,quartz, calcium, carbonate, magnesium oxide, carbon black, graphite,glass fibers, glass micro spheres, glass micro balloons, glass beads,carbon fibers, silicon carbide, polystyrene beads, microcrystallinecellulose, nanoparticles and metal fibers.
 16. An appliance according toone of claims 1-15, wherein the viscoelastic foam comprises anantimicrobial agent.
 17. An appliance according to claim 16, wherein theantimicrobial agent comprises one or more agents selected from the groupconsisting of silver salts, silver ions, silver ions encapsulated in aglass particle, silver sodium zirconium hydrogenphosphate,3-(Trimethoxysilyl)propyl dimethyl octadecyl ammonium chloride,benzalkonium chloride, benzethonium chloride, and chloroxylenol,polyhexamethylenebiguanide (PHMB) and chlorhexidine.
 18. An applianceaccording to one of claims 1-17, wherein (i) is true.
 19. An applianceaccording to one of claims 1-18, wherein (ii) is true.
 20. An applianceaccording to one of claims 1-19, wherein (iii) is true.
 21. An applianceaccording to one of claims 1-20, wherein (iv) is true.
 22. An applianceaccording to one of claims 1-21, wherein the appliance is an eyeprotection mask.
 23. An appliance according to one of claims 1-21,wherein the appliance is a SCUBA mask
 24. An appliance according to oneof claims 1-21, wherein the appliance is a swim goggle.
 25. An applianceaccording to claim 23 or 24, wherein the viscoelastic foam provides aseal to the tissue, and a water leakage past the seal such that at apressure of 1 atm, the appliance leaks no more than 10% of the internalvolume of the appliance in 10 minutes.
 26. An appliance according to oneof claims 1-21, wherein the appliance is a medical appliance.
 27. Anappliance according to one of claims 1-21, wherein the appliance is abreathing mask.
 28. An appliance according to one of claims 1-21,wherein the medical appliance is a negative pressure chamber configuredto cover tissue of a human or animal body.
 29. An appliance according toclaim 28, wherein the medical appliance is a negative-pressure woundtherapy device.
 30. An appliance according to claim 28, wherein thenegative pressure chamber is a continuous negative external pressure(cNEP) therapy device for maintenance of airway patency by theapplication of an external negative pressure to tissue overlying aportion of a human airway.
 31. An appliance according to one of claims1-21, wherein the appliance is a set of headphones, ear plugs, ear buds,or earphones.
 32. An appliance according to one of claims 1-21, whereinthe appliance is a catheter, a vascular stent, a vascular graft, avascular stent-graft, or components thereof.
 33. A method of forming aviscoelastic foam providing a tissue contact surface of an applianceaccording to one of claims 1-32, comprising: combining a silicone base,a foaming agent, and a catalyst to provide a formulation; curing theformulation under conditions selected to provide the viscoelastic foam,wherein the viscoelastic foam has one or more of the followingproperties: a Shore A of about 10 or less, and preferably a Shore 00durometer of about 30 or less, more preferably of about 20 or less, andstill more preferably of about 10 or less, in each case as measuredusing the Standard Test Method for Rubber Property—Durometer HardnessASTM D2240-15; a density (specific gravity) of about 0.9 g/cm³ or less;and/or a level of tack measured using the Standard Test Method forPressure-Sensitive Tack of Adhesives ASTM D2979-16 of about 9 mJ/cm² orless, preferably about 7 mJ/cm² or less, most preferably about 5 mJ/cm²or less; an elastic (storage) modulus of between about 0.3 kPa to about30 kPa, and preferably between about 1 kPa and about 15 kPa; a viscous(loss) modulus of between about 0.4 kPa to about 7 kPa, and preferablybetween about 0.8 kPa and about 7 kPa.
 34. A method according to claim33, wherein the curing step comprises curing at a temperature betweenabout 100° C. and about 250° C.
 35. A method according to claim 34,wherein the curing step comprises curing at a temperature of at leastabout 120° C.
 36. A method according to claim 34, wherein the curingstep comprises curing at a temperature of at least about 150° C.
 37. Amethod according to claim 34, wherein the curing step comprises curingat a temperature of at least about 170° C.
 38. A method according to oneof claims 33-37, wherein the foaming agent comprises an ammonium salt, asodium salt, or a potassium salt.
 39. A method according to one ofclaims 33-38, wherein the catalyst is selected from the group consistingof an iron catalyst, a cobalt catalyst, a zinc catalyst, a titanatecatalyst, a tin catalyst, a platinum catalyst, or an acid catalyst. 40.A method according to one of claims 33-39, wherein the viscoelastic foamcomprises one or both of an elastic (storage) modulus of between about10 kPa and about 15 kPa and a viscous (loss) modulus of between about 2kPa and about 7 kPa.
 41. A method according to claim 40, wherein theviscoelastic foam comprises a Shore A of about 10 or less, a density(specific gravity) of about 0.9 g/cm³ or less, and a level of tack ofabout 9 mJ/cm² or less.
 42. A method according to claim 41, wherein thefoam comprises a Shore A of about 5 or less.
 43. A method according toclaim 41, wherein the foam comprises a Shore A of about 1 or less.
 44. Amethod according to one of claims 33-43, wherein the viscoelastic foamdoes not include a tackifier or an adhesive.
 45. A method according toone of claims 33-44, wherein the viscoelastic foam exhibits a tack of atleast about 0.1 mJ/cm², at least about 0.3 mJ/cm², or at least about 0.5mJ/cm².
 46. A method according to one of claims 33-45, wherein an outersurface of the viscoelastic foam is skinned-over to form a closed cellregion of the viscoelastic foam.
 47. An appliance according to claim 46,wherein the viscoelastic foam is coated with a thin elastomer of lessthan 40 durometer and in ratios less than 1:10 to produce a dualdurometer structure.
 48. An appliance according to claim 46, wherein theviscoelastic foam is coated with a medical-grade SSA silicone of lessthan 40 durometer and in ratios less than 1:10 to produce a dualdurometer structure.
 49. A method according to one of claims 33-48,wherein the silicone base is an LSR.
 50. A method according to one ofclaims 33-48, wherein the silicone base is an HCR.
 51. A methodaccording to one of claims 33-50 wherein one or more of (i), (ii),(iii), and (iv) is true: (i) the tissue interface portion comprises asiloxane antimicrobial material coated onto or molded into theviscoelastic foam; (ii) the tissue interface portion is overmolded onthe noncontacting portion; (iii) the tissue interface portion isattached to the noncontacting portion using a siliconepressure-sensitive adhesive; and (iv) tissue interface portion comprisesone of more filler materials having a higher thermal conductivity thanthe viscoelastic foam material in the absence of the filler materials.52. An appliance according to claim 51, wherein (i) is true.
 53. Anappliance according to one of claim 51 or 52, wherein (ii) is true. 54.An appliance according to one of claims 51-53, wherein (iii) is true.55. An appliance according to one of claims 51-54, wherein (iv) is true.